c# - 无法从 ObservableCollection 转换为 ObservableCollection`1

Question

我为 ObservableCollection 构建了一个简单的扩展方法 AddRange:

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;

namespace Helpers
{

/// <summary>
/// Provides extension methods for the ObservableCollection<> class.
/// </summary>
public static class ObservableCollectionExtensions
{
    /// <summary>
    /// Adds a range of values to an ObservableCollection
    /// </summary>
    /// <typeparam name="T">The type of the collection.</typeparam>
    /// <param name="me">The observable collection to add values to.</param>
    /// <param name="values">The range of values to add.</param>
    public static void AddRange<T>(this ObservableCollection<T> me, IEnumerable<T> values)
    {
        foreach(var value in values)
        {
            me.Add(value);
        }
    }
}
}

我创建了一个测试类(使用 MSTest)如下:

using System;
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.ObjectModel;
using Helpers;
namespace Helpers.Tests
{
[TestClass()]
public class ObservableCollectionExtensionsTests
{
    [TestMethod()]
    public void AddRangeTest()
    {
        ObservableCollection<string> coll = new ObservableCollection<string>();
        coll.Add("Hello");
        coll.Add("World");
        IEnumerable<string> range = new List<string>() { "This", "Is", "A", "Test" };
        coll.AddRange(range); //This is the line that fails
        Assert.AreEqual("hello world this is a test", String.Join(" ", coll).ToLowerInvariant());
    }
}
}

但是，当我尝试构建我的项目时，出现以下错误:

Error   Instance argument: cannot convert from 'System.Collections.ObjectModel.ObservableCollection<string>' to 'System.Collections.ObjectModel.ObservableCollection`1<string>' C:\TigerTMS\projects\Tests\Helpers\Extensions\ObservableCollectionExtensionsTests.cs

Error   'System.Collections.ObjectModel.ObservableCollection<string>' does not contain a definition for 'AddRange' and the best extension method overload 'iCharge.Helpers.ObservableCollectionExtensions.AddRange<T>(System.Collections.ObjectModel.ObservableCollection`1<T>, System.Collections.Generic.IEnumerable<T>)' has some invalid arguments  C:\TigerTMS\projects\Tests\Helpers\Extensions\ObservableCollectionExtensionsTests.cs

Error   The type 'System.Collections.ObjectModel.ObservableCollection`1<T0>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Windows, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e'.    C:\TigerTMS\projects\Tests\Helpers\Extensions\ObservableCollectionExtensionsTests.cs

测试项目与扩展方法在同一个解决方案中，我能够在该解决方案中的其他项目中毫无问题地使用扩展方法。此外，没有警告。

我已经尝试检查以确保它们都使用相同版本的 .NET，并且我没有使用来自不同库的一些错误版本的 ObservableCollection，但这没有效果我想不出下一步该去哪里。

编辑:在构建输出下，我收到以下警告:

7>------ Build started: Project: iChargeTests, Configuration: Debug Any CPU ------
7>  No way to resolve conflict between "System.Xml, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" and "System.Xml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089". Choosing "System.Xml, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" arbitrarily.
7>  No way to resolve conflict between "System.ComponentModel.DataAnnotations, Version=5.0.5.0, Culture=neutral, PublicKeyToken=ddd0da4d3e678217" and "System.ComponentModel.DataAnnotations, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35". Choosing "System.ComponentModel.DataAnnotations, Version=5.0.5.0, Culture=neutral, PublicKeyToken=ddd0da4d3e678217" arbitrarily.
7>  No way to resolve conflict between "System.Runtime.Serialization, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" and "System.Runtime.Serialization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089". Choosing "System.Runtime.Serialization, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" arbitrarily.
7>  No way to resolve conflict between "System.ServiceModel, Version=5.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" and "System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089". Choosing "System.ServiceModel, Version=5.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" arbitrarily.

但是，由于它们都不是 ObservableCollection (System.Collections.ObjectModel) 的命名空间，我可以忽略它们吗？

编辑 2: 在我的测试项目中添加了对 System.Windows 的引用，并在测试类中添加了行 using System.Windows ，错误仍然存​​在。

Answer 1

所以我正在处理同样的问题 ( Generics: How to resolve conflicting ObservableCollection classes? )，我想我至少知道为什么这不起作用。我寻求的解决方案并不理想，但也可能适合您。

首先，核心问题:Silverlight 使用的 ObservableCollection 不是标准的 WPF。如果您查看这两个程序集，您会发现它们有很多不同的接口(interface)。这是 windows/服务器使用的:

Assembly System.dll, v4.0.30319

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Runtime;
using System.Runtime.CompilerServices;

namespace System.Collections.ObjectModel
{
    [Serializable]
    [TypeForwardedFrom("WindowsBase, Version=3.0.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
    public class ObservableCollection<T> : Collection<T>, INotifyCollectionChanged, INotifyPropertyChanged
    {
        // Implementation
    }

这是 Silverlight 使用的版本:

Assembly System.Windows.dll, v4.0.30319
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;

namespace System.Collections.ObjectModel
{
    public class ObservableCollection<T> : Collection<T>, INotifyCollectionChanged, INotifyPropertyChanged
    {
        // Implmentation
    }
}

因此，它们无法转换也就不足为奇了。我追求的解决方案是创建一个单独的对象，它实现了两者所需的核心接口(interface)(Collection、INotifyCollectionChanged、INotifyPropertyChanged)并使用它而不是 ObservableCollection 类。希望这可以帮助您找到更好的解决方案。如果你这样做，请告诉我!