C#泛型滥用？

Question

我不明白为什么会出现错误 cannot be used as type parameter 't' in the generic type or method...There is no implicit reference conversion from...

这是我的全部代码(已简化):

问题出在RefreshLocalListFromLocalStore(TestDataObjectTable);

这行上

using System;
using Microsoft.WindowsAzure.MobileServices;
using Microsoft.WindowsAzure.MobileServices.SQLiteStore;
using Microsoft.WindowsAzure.MobileServices.Sync;

public class TestDataObject
{
    #region Properties

    public string Id { get; set; }

    #endregion
}

public class TestDatabaseManager
{
    public MobileServiceClient Client;

    private IMobileServiceSyncTable<TestDataObject> TestDataObjectTable;

    public TestDatabaseManager()
    {
        CurrentPlatform.Init();
        Client = new MobileServiceClient("SomeUrl");
        var store = new MobileServiceSQLiteStore("SomePath");
        store.DefineTable<TestDataObject>();

        TestDataObjectTable = Client.GetSyncTable<TestDataObject>();

        RefreshLocalListFromLocalStore(TestDataObjectTable);
    }

    #region Methods

    public async void RefreshLocalListFromLocalStore<T>(T table) where T : IMobileServiceSyncTable<T>
    {
        try
        {
            await table.ToListAsync();
        }
        catch (Exception e)
        {
        }
    }

    #endregion
}

Answer 1

您的通用约束可能是错误的。对 RefreshLocalListFromLocalStore 使用以下声明:

public async void RefreshLocalListFromLocalStore<T>(IMobileServiceSyncTavble<T> table)

在你的声明中，表格应该是表格的表格，这是没有意义的。您仍然可以使用泛型约束来限制您希望表中的元素类型，例如，如果表中的元素应该是符合某些 IEntity 接口(interface)的实体。

public async void RefreshLocalListFromLocalStore<T>(IMobileServiceSyncTavble<T> table) where T : IEntity