I had this discussion many times over the last few years:
Opinions on this subject vary a lot. This purpose of this article is to provide you some basic guidelines and why you should follow them.
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The WordPress.com stats helper monkeys prepared a 2012 annual report for this blog.
Here’s an excerpt:
4,329 films were submitted to the 2012 Cannes Film Festival. This blog had 24,000 views in 2012. If each view were a film, this blog would power 6 Film Festivals
Select method is used to project each element of a sequence into a new form, i.e. it can be used to map a collection of one type to a collection of another type. In this article I’ll show you a simple approach that will allow you to reuse the code used in the Select method.
Table of contents
Consider the following model:
Let’s suppose that you have a services layer, so you don’t want to expose your domain objects directly to the client applications. Instead you create a set of data contracts (or DTOs, if you prefer):
At some stage you’ll have to convert those Domain objects to data contracts. This is a common way of doing it:
var details = repository.All<Album>().Select(album => new AlbumDetail {
AlbumId = album.AlbumId,
Price = album.Price,
Title = album.Title,
ArtistId = album.ArtistId,
GenreId = album.GenreId,
ArtistName = (album.Artist == null) ? null : album.Artist.Name,
GenreName = (album.Genre == null) ? null : album.Genre.Name
});
There is a problem with this approach – if you need to query the same collection but using different criteria you have to duplicate the code inside the Select method.
In order to reuse the code, we can create a method that converts Album objects (Domain) to data contract objects:
private static AlbumSummary CreateAlbumSummary(Album album)
{
return new AlbumSummary {
AlbumId = album.AlbumId,
Title = album.Title,
ArtistName = (album.Artist == null) ? null : album.Artist.Name
};
}
private static AlbumDetail CreateAlbumDetail(Album album)
{
return new AlbumDetail {
AlbumId = album.AlbumId,
Price = album.Price,
Title = album.Title,
ArtistId = album.ArtistId,
GenreId = album.GenreId,
ArtistName = (album.Artist == null) ? null : album.Artist.Name,
GenreName = (album.Genre == null) ? null : album.Genre.Name
};
}
Using the code:
var albums = Albums.Select(CreateAlbumDetail); var albumsByGenre = Albums.Where(x => x.GenreId == genreId).Select(CreateAlbumDetail); // alternative way var albums2 = Albums.Select(x => CreateAlbumDetail(x)); var albumsByGenre2 = Albums.Where(x => x.GenreId == genreId).Select(x => CreateAlbumDetail(x));
The previous solution solves the code reusability problem, but there’s still a tight coupling between components. Abstractions should be used to implement loose coupling between components – in this case, to abstract the mapping code.
Step 1: define a contract (interface) with a method that converts one object of type TSource to an object of type TDestination:
public interface IObjectMapper
{
TDestination Map<TSource, TDestination>(TSource source);
}
Step 2: create a class that implements IObjectMapper (click to expand):
public class ObjectMapper : IObjectMapper
{
private Dictionary<Type, Func<object, object>> Mappers = new Dictionary<Type, Func<object, object>>
{
{ typeof(Tuple<Album, AlbumDetail>), CreateAlbumDetail },
{ typeof(Tuple<Album, AlbumSummary>), CreateAlbumSummary }
// more mappings here
// ....
};
public TDestination Map<TSource, TDestination>(TSource source)
{
if(source == null)
return default(TDestination);
Func<object, object> mapper = null;
Type key = typeof(Tuple<TSource, TDestination>);
if(Mappers.TryGetValue(key, out mapper))
{
var newObject = mapper(source);
return (TDestination) newObject;
}
string errorMessage = string.Format("Invalid mapping (Source: {0}, Destination: {1})";,
typeof(TSource).FullName,
typeof(TDestination).FullName);
throw new InvalidOperationException(errorMessage);
}
private static object CreateAlbumDetail(object source)
{
var album = source as Album;
return new AlbumDetail {
AlbumId = album.AlbumId,
Price = album.Price,
Title = album.Title,
ArtistId = album.ArtistId,
GenreId = album.GenreId,
ArtistName = (album.Artist == null) ? null : album.Artist.Name,
GenreName = (album.Genre == null) ? null : album.Genre.Name
};
}
private static object CreateAlbumSummary(object source)
{
var album = source as Album;
return new AlbumSummary {
AlbumId = album.AlbumId,
Title = album.Title,
ArtistName = (album.Artist == null) ? null : album.Artist.Name
};
}
}
Using the mapper in a LINQ expression – convert an Album collection to an AlbumSummary collection:
IObjectMapper mapper = new ObjectMapper();
IEnumerable<AlbumSummary> summaries = repository.All<Album>()
.Select(mapper.Map<Album, AlbumSummary>);
Using the mapper for a single object:
var album = new Album {
AlbumId = 1,
Price = 10.0m,
Title = "The Dreamer",
Artist = new Artist { ArtistId = 1, Name = "José James" },
Genre = new Genre { GenreId = 1, Name = "Jazz" }
};
IObjectMapper mapper = new ObjectMapper();
AlbumDetail albumDetail = mapper.Map<Album, AlbumDetail>(album);
Some NUnit tests:
[Test]
public void Given_a_non_existing_mapping_when_mapping_object_then_should_throw_InvalidOperationException()
{
// arrange
IObjectMapper mapper = new ObjectMapper();
var albumDetail = new AlbumDetail();
// act/assert
Assert.Throws<InvalidOperationException>(() =>
// non-existing mapping
mapper.Map<AlbumDetail, AlbumSummary>(albumDetail)
);
}
[Test]
public void Given_an_album_when_mapping_to_album_summary_should_equals_expected_album_summary()
{
// arrange
IObjectMapper mapper = new ObjectMapper();
var album = new Album {
AlbumId = 4,
Price = 10.0m,
Title = "Heritage",
Artist = new Artist { ArtistId = 4, Name = "Opeth" },
Genre = new Genre { GenreId = 4, Name = "Metal" }
};
var expectedAlbumSummary = new AlbumSummary {
AlbumId = 4,
ArtistName = "Opeth",
Title = "Heritage"
};
// act
AlbumSummary albumSummary = mapper.Map<Album, AlbumSummary>(album);
// assert
Assert.AreEqual(albumSummary, expectedAlbumSummary);
}
In this article you learned how to reuse the code used in the Select method, and how you can use that code to map single objects. But writing mapping code is tedious and time consuming. There are mapping tools out there that can make your life easier – AutoMapper is one of them. I’ve used it in the past and I definitely recommend it. So, why use Automapper? Quoting their website:
“What makes AutoMapper interesting is that it provides some interesting conventions to take the dirty work out of figuring out how to map type A to type B. As long as type B follows AutoMapper’s established convention, almost zero configuration is needed to map two types”
“Mapping code is boring. Testing mapping code is even more boring. AutoMapper provides simple configuration of types, as well as simple testing of mappings”
Download the demo project (VS2010): LINQ-Select.zip
This table was in a database of a company where I worked some years ago.
I can’t think of any reason someone would create a table like this one, can you?
This is the first of a 2 series articles about how to perform bulk inserts in your .NET applications, using a SQL Server database.
In this article I’ll show how to create a wrapper object for SqlBulkCopy that can do a bulk insert for a collection of objects. In the second article I’ll show how that wrapper can be easily integrated with Entity Framework (creating extension methods for DbContext and ObjectContext).
Table of contents
I am working in an application that parses Excel files and creates an object for each line. After some validations and properties mapping the objects are then being inserted in a database table, one by one. At the beggining this wasn’t a big problem because the number of objects to insert in the database was small, but now there can be files with thousands of rows, so using Entity Framework isn’t the best way to do it (currently Entity Framework has no support for bulk insert operations).
I decided to use the object SqlBulkCopy because it seemed the best and easiest option for performing a bulk insert in a SQL Server database. I created a wrapper for SqlBulkCopy – BulkCopy.cs. This class works the same way as SqlBulkCopy but has some extra features.
The following properties are available:
And these are the methods available (see examples below):
public void WriteToServer<T>(IEnumerable<T> items) where T : class; public void WriteToServer<T>(IEnumerable<T> items, SqlBulkCopyOptions options) where T : class; public void WriteToServer<T>(IEnumerable<T> items, SqlBulkCopyOptions options, IEnumerable<SqlBulkCopyColumnMapping> columnMappings) where T : class;
BulkCopy.cs source code (click to expand):
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data.SqlClient;
using System.Data;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using BulkCopy.Extensions;
namespace BulkCopy
{
/// <summary>
/// Lets you efficiently bulk load a SQL Server table with data from another source.
/// This is a wrapper class for <see cref="SqlBulkCopy"/>
/// </summary>
public class BulkCopy
{
/// <summary>
/// Name of the destination table on the server
/// </summary>
public string DestinationTableName { get; set; }
/// <summary>
/// Number of rows in each batch.
/// At the end of each batch, the rows in the batch are sent to the server.
/// </summary>
public int? BatchSize { get; set; }
/// <summary>
/// Database connection string
/// </summary>
public string ConnectionString { get; set; }
/// <summary>
/// Filters the properties to be included
/// </summary>
public Func<PropertyDescriptor, bool> ExpressionFilter { get; set; }
/// <summary>
/// Initializes a new instance of the <see cref="BulkCopy<T>"/> class.
/// </summary>
public BulkCopy()
{
}
/// <summary>
/// Initializes a new instance of the <see cref="BulkCopy<T>"/> class.
/// </summary>
public BulkCopy(string connectionString)
{
this.ConnectionString = connectionString;
}
/// <summary>
/// Copies all items in a collection to a destination table
/// </summary>
/// <param name="dataTable">The items that will be copied to the destination table</param>
/// <param name="options">A combination of values from the System.Data.SqlClient.SqlBulkCopyOptions
/// enumeration that determines which data source rows are copied to the destination table. <see cref="SqlBulkCopyOptions"/></param>
public virtual void WriteToServer<T>(IEnumerable<T> items) where T : class
{
WriteToServer(items, SqlBulkCopyOptions.Default);
}
/// <summary>
/// Copies all items in a collection to a destination table
/// </summary>
/// <param name="dataTable">The items that will be copied to the destination table</param>
/// <param name="options">A combination of values from the System.Data.SqlClient.SqlBulkCopyOptions
/// enumeration that determines which data source rows are copied to the destination table. <see cref="SqlBulkCopyOptions"/></param>
public virtual void WriteToServer<T>(IEnumerable<T> items, SqlBulkCopyOptions options) where T : class
{
DataTable dataTable = (this.ExpressionFilter == null) ? items.ToDataTable() : items.ToDataTable(this.ExpressionFilter);
WriteToServer(dataTable, options);
}
/// <summary>
/// Copies all items in a collection to a destination table
/// </summary>
/// <param name="dataTable">The items that will be copied to the destination table</param>
/// <param name="options">A combination of values from the System.Data.SqlClient.SqlBulkCopyOptions
/// enumeration that determines which data source rows are copied to the destination table. <see cref="SqlBulkCopyOptions"/></param>
/// <param name="columnMappings">Returns a collection of System.Data.SqlClient.SqlBulkCopyColumnMapping items.
/// Column mappings define the relationships between columns in the data source and columns in the destination.</param>
public virtual void WriteToServer<T>(IEnumerable<T> items, SqlBulkCopyOptions options, IEnumerable<SqlBulkCopyColumnMapping> columnMappings) where T : class
{
DataTable dataTable = (this.ExpressionFilter == null) ? items.ToDataTable() : items.ToDataTable(this.ExpressionFilter);
WriteToServer(dataTable, options, columnMappings);
}
/// <summary>
/// Copies all rows in the supplied System.Data.DataTable to a destination table
/// </summary>
/// <param name="dataTable">A System.Data.DataTable whose rows will be copied to the destination table</param>
private void WriteToServer(DataTable dataTable)
{
WriteToServer(dataTable, SqlBulkCopyOptions.Default);
}
/// <summary>
/// Copies all rows in the supplied System.Data.DataTable to a destination table
/// </summary>
/// <param name="dataTable">A System.Data.DataTable whose rows will be copied to the destination table</param>
/// <param name="options">A combination of values from the System.Data.SqlClient.SqlBulkCopyOptions
/// enumeration that determines which data source rows are copied to the destination table. <see cref="SqlBulkCopyOptions"/></param>
private void WriteToServer(DataTable dataTable, SqlBulkCopyOptions options)
{
var columnMappings = from x in dataTable.Columns.Cast<DataColumn>()
select new SqlBulkCopyColumnMapping(x.ColumnName, x.ColumnName);
WriteToServer(dataTable, options, columnMappings);
}
/// <summary>
/// Copies all rows in the supplied System.Data.DataTable to a destination table
/// </summary>
/// <param name="dataTable">A System.Data.DataTable whose rows will be copied to the destination table</param>
/// <param name="options">A combination of values from the System.Data.SqlClient.SqlBulkCopyOptions
/// enumeration that determines which data source rows are copied to the destination table. <see cref="SqlBulkCopyOptions"/></param>
/// <param name="columnMappings">Returns a collection of System.Data.SqlClient.SqlBulkCopyColumnMapping items.
/// Column mappings define the relationships between columns in the data source and columns in the destination.</param>
private void WriteToServer(DataTable dataTable, SqlBulkCopyOptions options, IEnumerable<SqlBulkCopyColumnMapping> columnMappings)
{
// table name matching:
// checks for DestinationTableName value
// if null or empty, checks for dataTable.TableName
string destinationTableName =
(string.IsNullOrWhiteSpace(DestinationTableName) ? null : DestinationTableName)
?? (string.IsNullOrWhiteSpace(dataTable.TableName) ? null : dataTable.TableName);
if(string.IsNullOrWhiteSpace(destinationTableName))
throw new ArgumentException("destinationTableName cannot be null or empty");
using(var bulkCopy = new SqlBulkCopy(this.ConnectionString, options))
{
bulkCopy.DestinationTableName = destinationTableName;
if(this.BatchSize.HasValue)
bulkCopy.BatchSize = this.BatchSize.Value;
foreach(var mapping in columnMappings)
bulkCopy.ColumnMappings.Add(mapping);
bulkCopy.WriteToServer(dataTable);
}
}
}
}
The BulkCopy object is using internally some extension methods that converts a collection of objects to a DataTable. (taken from SO’s post Generic List to DataTable, with some small modifications).
Click to expand the source code:
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Data;
using System.ComponentModel;
namespace BulkCopy.Extensions
{
public static class DataExtensions
{
/// <summary>
/// Basic data types
/// </summary>
private static Type[] dataTypes = new[] {
typeof(byte)
,typeof(sbyte)
,typeof(short)
,typeof(ushort)
,typeof(int)
,typeof(uint)
,typeof(long)
,typeof(ulong)
,typeof(float)
,typeof(double)
,typeof(decimal)
,typeof(bool)
,typeof(char)
,typeof(Guid)
,typeof(DateTime)
,typeof(DateTimeOffset)
,typeof(byte[])
,typeof(string)
};
/// <summary>
/// Converts a generic List to a DataTable
/// <see cref="http://stackoverflow.com/a/5805044"/>
/// </summary>
/// <typeparam name="T">Type of the object to convert to DataTable</typeparam>
/// <param name="data">Data to be converted</param>
/// <returns>The converted DataTable</returns>
public static DataTable ToDataTable<T>(this IList<T> data)
{
IEnumerable<PropertyDescriptor> properties = from x in TypeDescriptor.GetProperties(typeof(T)).Cast<PropertyDescriptor>()
where IsBasicType(x.PropertyType)
select x;
DataTable table = GetDataTable(data, properties);
return table;
}
/// <summary>
/// Converts a generic List to a DataTable
/// <see cref="http://stackoverflow.com/a/5805044"/>
/// </summary>
/// <typeparam name="T">Type of the object to convert to DataTable</typeparam>
/// <param name="data">Data to be converted</param>
/// <returns>The converted DataTable</returns>
public static DataTable ToDataTable<T>(this IList<T> data, Func<PropertyDescriptor, bool> expression)
{
var properties = TypeDescriptor.GetProperties(typeof(T))
.Cast<PropertyDescriptor>()
.Where(expression);
DataTable table = GetDataTable(data, properties);
return table;
}
/// <summary>
/// Converts an IEnumerable to a DataTable
/// <see cref="http://stackoverflow.com/a/5805044"/>
/// </summary>
/// <typeparam name="T">Type of the object to convert to DataTable</typeparam>
/// <param name="data">Data to be converted</param>
/// <returns>The DataTable</returns>
public static DataTable ToDataTable<T>(this IEnumerable<T> data)
{
return data.ToList().ToDataTable();
}
/// <summary>
/// Converts an IEnumerable to a DataTable
/// <see cref="http://stackoverflow.com/a/5805044"/>
/// </summary>
/// <typeparam name="T">Type of the object to convert to DataTable</typeparam>
/// <param name="data">Data to be converted</param>
/// <param name="expression">Predicate to filter the properties of <typeparamref name="T"/> to be included to the DataTable</param>
/// <returns>The DataTable</returns>
public static DataTable ToDataTable<T>(this IEnumerable<T> data, Func<PropertyDescriptor, bool> expression)
{
return data.ToList().ToDataTable(expression);
}
#region Private methods
private static bool IsBasicType(Type type)
{
type = Nullable.GetUnderlyingType(type) ?? type;
return type.IsEnum || dataTypes.Contains(type);
}
private static DataTable GetDataTable<T>(this IList<T> data, IEnumerable<PropertyDescriptor> mappedProperties)
{
DataTable table = new DataTable();
// columns
foreach(PropertyDescriptor prop in mappedProperties)
{
table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
}
// row values
foreach(T item in data)
{
DataRow row = table.NewRow();
foreach(PropertyDescriptor prop in mappedProperties)
{
object value = prop.GetValue(item) ?? DBNull.Value;
row[prop.Name] = value;
}
table.Rows.Add(row);
}
return table;
}
#endregion
}
}
Assuming a table named dbo.Albums (I’m using Mvc Music Store model):
This example shows how to use a model object whose property names match the database column names from the table above:
public class Album
{
public virtual int AlbumId { get; set; }
public virtual int GenreId { get; set; }
public virtual int ArtistId { get; set; }
public virtual string Title { get; set; }
public virtual decimal Price { get; set; }
public virtual string AlbumArtUrl { get; set; }
}
All you need to do is to specify the connection string and the destination table:
IEnumerable<Album> data = GetData();
var bulkCopy = new BulkCopy() {
ConnectionString = ConnectionString,
DestinationTableName = "dbo.Albums"
};
bulkCopy.WriteToServer(data);
Using the model from the previous example, you can specify some other options:
IEnumerable<Album> data = GetData();
var bulkCopy = new BulkCopy() {
BatchSize = 200,
ConnectionString = ConnectionString,
DestinationTableName = "dbo.Albums"
};
// SqlBulkCopyOptions.CheckConstraints: Check constraints while data is being inserted.
// By default, constraints are not checked.
bulkCopy.WriteToServer(data, SqlBulkCopyOptions.CheckConstraints);
This example shows how to use a model object whose property names don’t match the database column names:
public class Album
{
public virtual int Id { get; set; }
public virtual int GenreId { get; set; }
public virtual int ArtistId { get; set; }
public virtual string AlbumTitle { get; set; }
public virtual decimal Price { get; set; }
public virtual string AlbumArtImage { get; set; }
}
In this case we have to create the column mappings. It can be done like this:
private static IEnumerable<SqlBulkCopyColumnMapping> GetColumnMappings()
{
yield return new SqlBulkCopyColumnMapping("Id", "AlbumId");
yield return new SqlBulkCopyColumnMapping("GenreId", "GenreId");
yield return new SqlBulkCopyColumnMapping("ArtistId", "ArtistId");
yield return new SqlBulkCopyColumnMapping("AlbumTitle", "Title");
yield return new SqlBulkCopyColumnMapping("Price", "Price");
yield return new SqlBulkCopyColumnMapping("AlbumArtImage", "AlbumArtUrl");
}
Finally, the bulk insert can be done this way:
IEnumerable<Album> data = GetData();
IEnumerable<SqlBulkCopyColumnMapping> mappings = GetColumnMappings();
var bulkCopy = new BulkCopy() {
ConnectionString = ConnectionString,
DestinationTableName = "dbo.Albums"
};
bulkCopy.WriteToServer(data,SqlBulkCopyOptions.Default, mappings);
This example shows how to filter the properties of a model object to be used in the bulk insert:
public partial class Album
{
public virtual int AlbumId { get; set; }
public virtual int GenreId { get; set; }
public virtual int ArtistId { get; set; }
public virtual string Title { get; set; }
public virtual decimal Price { get; set; }
public virtual string AlbumArtUrl { get; set; }
public virtual string P1 { get; set; }
public virtual string P2 { get; set; }
}
Properties P1 and P2 don’t match any column of the table above, so they cannot be used in the bulk insert operation. Creating a filter to exclude those properties and using it can be done like this:
// properties to exclude from mapping
var nonMappedProperties = new string[] { "P1", "P2" };
Func<PropertyDescriptor, bool> expression = x =>
!nonMappedProperties.Contains(x.Name);
IEnumerable<Album> data = GetData();
var bulkCopy = new BulkCopy() {
BatchSize = 200,
ConnectionString = ConnectionString,
DestinationTableName = "dbo.Albums",
ExpressionFilter = expression
};
bulkCopy.WriteToServer(data, SqlBulkCopyOptions.CheckConstraints);
That’s it! In the next article I’ll show you how to integrate easily this wrapper class in Entity Framework (creating extension methods for DbContext and ObjectContext).
Download the demo project (VS2010): BulkCopy-part1.zip
Extension methods for ObjectContext and DbContent to get the mapped table name from an entity.
Table of contents
I am working on a set of extension methods to perform a bulk insert using Entity Framework, using internally the SqlBulkCopy object. One of the steps involved is to get the mapped table name from an entity. After some google searching, I found a post on StackOverflow that led me to the solution.
The trick is to use the method ObjectQuery.ToTraceString to generate a SQL Select statement for an entity, and then extract the table name from that statement.
Let’s assume that you have an entity named Album corresponding to a table named dbo.Albums.
// context is ObjectContext string sql = context.CreateObjectSet<T>().ToTraceString(); ...
The generated SQL for that entity can be something like this:
SELECT [Extent1].[AlbumId] AS [AlbumId], [Extent1].[GenreId] AS [GenreId], [Extent1].[ArtistId] AS [ArtistId], [Extent1].[Title] AS [Title], [Extent1].[Price] AS [Price], [Extent1].[AlbumArtUrl] AS [AlbumArtUrl] FROM [dbo].[Albums] AS [Extent1]
So, all we need to do is to parse the SELECT statement to get the table name. This is the approach used in the post above but it has some limitations – that code will work only for tables that are in the default SQL Server schema (dbo.{tableName}). I made some changes to that code and I’m extracting the full table name using regular expressions.
I have created one extension method for DbContext and other for ObjectContext:
public static class ContextExtensions
{
public static string GetTableName<T>(this DbContext context) where T : class
{
ObjectContext objectContext = ((IObjectContextAdapter) context).ObjectContext;
return objectContext.GetTableName<T>();
}
public static string GetTableName<T>(this ObjectContext context) where T : class
{
string sql = context.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex("FROM (?<table>.*) AS");
Match match = regex.Match(sql);
string table = match.Groups["table"].Value;
return table;
}
}
Getting the mapped table name for an entity named Album, using a ObjectContext object:
ObjectContext context = ....; string table = context.GetTableName<Album>();
Or using a DbContext object:
DbContext context = ....; string table = context.GetTableName<Album>();
A collection of HTML helpers that generate DropDownlists for enums, with or without localization support.
Table of contents
I’ve created a set of HTML helpers that generate a DropDownList for an enum.
Those helpers are similar to DropDownList Method and DropDownListFor Method, with the only difference being that the those helpers will populate the DropDownList with the elements of the specified enum.
Let’s assume the following model:
public enum WeekDay
{
Sunday,
Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday
}
public class WeeklyEvent
{
public string Title { get; set; }
public WeekDay Day { get; set; }
public WeekDay? AnotherDay { get; set; }
}
This is the most basic usage, the generated text will be enumValue.ToString():
// name="eventDay"
@Html.EnumDropDownList<WeekDay>("eventDay", "Select an item")
// name="Day"
@Html.EnumDropDownListFor<WeeklyEvent, WeekDay>(x => x.Day, "Select an item")
Html.EnumDropDownListFor works with nullables too:
@Html.EnumDropDownListFor<WeeklyEvent, WeekDay?>(x => x.AnotherDay, "Select an item")
You can customize the text using DescriptionAttribute:
public enum WeekDay
{
[Description("Domingo")]
Sunday,
[Description("Segunda")]
Monday,
[Description("Terça")]
Tuesday,
[Description("Quarta")]
Wednesday,
[Description("Quinta")]
Thursday,
[Description("Sexta")]
Friday,
[Description("Sábado")]
Saturday
}
Just like DropDownList and DropDownListFor, you can use custom HTML attributes
@Html.EnumDropDownList<WeekDay>("eventDay", "Select an item", new { @class="select"})
@Html.EnumDropDownListFor<WeeklyEvent, WeekDay>(x => x.Day, "Select an item" , new { @class="select"})
Implementing a cross-browser solution for downloading files from a UNC share in ASP.NET applications
Table of contents
I was working recently in an intranet application that had a download page. The output HTML was similar to the following:
<li><a class="download" href="\\MYSERVER\reports 2011\report1.zip" title="Report 1">Report 1</a></li> <li><a class="download" href="\\MYSERVER\reports 2011\report2.zip" title="Report 2">Report 2</a></li> <li><a class="download" href="\\MYSERVER\reports 2011\report 3.zip" title="Report 3">Report 3</a></li> <li><a class="download" href="\\MYSERVER\reports 2011\report 4.zip" title="Report 4">Report 4</a></li> <li><a class="download" href="\\MYSERVER\reports 2011\report 5&6.zip" title="Report 5&6">Report 5&6</a></li>
This was working fine in IE9, but not in other browsers. There was no action using Google Chrome, and using Firefox there was an error (HTTP Error 400 – Bad Request).
I tried to convert the file path to a file URI but it didn’t fix it. It continued to work on IE only.
<li><a class="download" href="file://MYSERVER/reports 2011/report1.zip" title="Report 1">Report 1</a></li> <li><a class="download" href="file://MYSERVER/reports 2011/report2.zip" title="Report 2">Report 2</a></li> <li><a class="download" href="file://MYSERVER/reports 2011/report 3.zip" title="Report 3">Report 3</a></li> <li><a class="download" href="file://MYSERVER/reports 2011/report 4.zip" title="Report 4">Report 4</a></li> <li><a class="download" href="file://MYSERVER/reports 2011/report 5&6.zip" title="Report 5&6">Report 5&6</a></li>
The solution was to create a custom ASP.NET download page. I used also jquery on the client side.
The first step was to add an event handler to the download links. The request URI is encoded and is sent as a parameter to the download page. Creating an hidden iframe and setting the src attribute with the download link allows the file to be downloaded asynchronously.
$("a.download").bind("click", function (e) {
e.preventDefault();
var requestedFile = encodeURIComponent($(this).attr('href'));
var iframe = document.createElement("iframe");
iframe.src = 'Download.aspx?file=' + requestedFile;
iframe.style.display = "none";
document.body.appendChild(iframe); // triggers download page
});
Make sure you use encodeURIComponent function to encode special characters in the filename.
This is the source code of the download page:
protected void Page_Load(object sender, EventArgs e)
{
try
{
string requestFile = Request.QueryString["file"];
if(string.IsNullOrEmpty(requestFile))
{
throw new FileNotFoundException("File to download cannot be null or empty");
}
// Get file name from URI string in C#
// http://stackoverflow.com/a/1105614
var uri = new Uri(requestFile);
string filename = Path.GetFullPath(uri.LocalPath);
var fileInfo = new FileInfo(filename);
if(!fileInfo.Exists)
{
throw new FileNotFoundException("File to download was not found", filename);
}
// get content type based on file extension. Example:
// http://stackoverflow.com/a/691599
Response.ContentType = GetContentType(fileInfo.Extension);
Response.AddHeader("Content-Disposition",
"attachment; filename=\"" + fileInfo.Name + "\"");
Response.WriteFile(fileInfo.FullName);
Response.End();
}
catch(ThreadAbortException)
{
// ignore exception
}
catch(FileNotFoundException ex)
{
Response.StatusCode = (int) System.Net.HttpStatusCode.NotFound;
Response.StatusDescription = ex.Message;
}
catch(Exception ex)
{
Response.StatusCode = (int) System.Net.HttpStatusCode.InternalServerError;
Response.StatusDescription = string.Format("Error downloading file: {0}", ex.Message);
}
}
Some notes:
This is necessary in order to make the download work with a UNC share (\\MYSERVER\….) or a file URI (file://….)
var uri = new Uri(requestFile);
string filename = Path.GetFullPath(uri.LocalPath);
To avoid filename truncating, it’s necessary to wrap the filename with quotes
Response.AddHeader("Content-Disposition",
"attachment; filename=\"" + fileInfo.Name + "\"");
The WordPress.com stats helper monkeys prepared a 2011 annual report for this blog.
Here’s an excerpt:
The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 14,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 5 sold-out performances for that many people to see it.
Recently, I had to setup Unity IoC container in an existing ASP.NET 3.5 Web Forms application. This application had not only web pages (.aspx files), but also some Web Services (.asmx files). After some research, I found out David Hayden’s screencast: Unity IoC and ASP.NET screencast – Dependency Injection into Web Pages.
You can use a similar technique for your Web Services – that’s what I’ll show you in this article.
Table of contents
You have the following interface and its implementation:
public interface ILogger
{
void Write(string message);
}
public class DebugLogger : ILogger
{
public void Write(string message)
{
Debug.WriteLine(message);
}
}
The first step is to setup Unity Container in Global.asax file. This is a good place to do it because it can be accessed either by web pages or by web services.
The CreateContainer() method is the place where the dependencies are specified.
public class Global : HttpApplication, IContainerAccessor
{
private static IUnityContainer _container;
public static IUnityContainer Container
{
get
{
return _container;
}
private set
{
_container = value;
}
}
IUnityContainer IContainerAccessor.Container
{
get
{
return Container;
}
}
protected void Application_Start(object sender, EventArgs e)
{
CreateContainer();
}
protected virtual void CreateContainer()
{
IUnityContainer container = new UnityContainer();
container.RegisterType<ILogger, DebugLogger>();
Container = container;
}
}
Create a generic BaseService that all your services will inherit from. The dependencies will be injected when you create an instance of the service (default constructor).
public abstract class BaseService<T> : System.Web.Services.WebService where T : class
{
public BaseService()
{
InjectDependencies();
}
protected virtual void InjectDependencies()
{
HttpContext context = HttpContext.Current;
if (context == null)
return;
IContainerAccessor accessor = context.ApplicationInstance as IContainerAccessor;
if (accessor == null)
return;
IUnityContainer container = accessor.Container;
if (container == null)
throw new InvalidOperationException("Container on Global Application Class is Null. Cannot perform BuildUp.");
container.BuildUp(this as T);
}
}
Now all you need to do is to inherit from the BaseService and invoke its base constructor.
Don’t forget to add the [Dependency] attribute to your dependency, and it has to be public.
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class DummyService : BaseService<DummyService>
{
[Dependency]
public ILogger Logger
{
get;
set;
}
public DummyService() : base()
{
}
[WebMethod]
public string HelloWorld(string name)
{
string message = string.Format("Hello World, {0}!", name);
this.Logger.Write(message);
return message;
}
}
That’s it! Now you just need to compile and run the application and see it in action 
Feel free to download the demo application
Download the demo project (VS2010): UnityAsmxWebServices.zip
