.net – 我可以在不实际执行的情况下测试LINQ查询的构造

为什么我们不能在没有实际执行的情况下对查询的构造进行单元测试？我原本以为你可以将你的IQueryable以某种方式附加到LINQ to Entities提供程序并确认SQL是否正确生成(使用ToTraceString这样不执行实际查询的东西).

我想象沿着这些行的代码(这个查询在L2O中运行良好但在L2E中运行不正常)：

<Test()> _
    Public Sub Query_Should_Build_Against_L2E()
        Dim testQuery = From d In myDb
                        Where d.Status = CType(Status.Ready,Integer)

        testQuery.SetQueryProvider("L2E")

        Assert.DoesNotThrow(testQuery.ToTraceString())
    End Sub

编辑

我尝试实现GertArnold的解决方案如下：

Dim context As New Context("Data Source=fakedbserver;Initial Catalog=fakedb;Persist Security Info=True;")
Dim result = context.myTable.Where(Function(d) d.Status=True)

抛出ProviderIncompatibleException,并显示消息“从数据库获取提供程序信息时发生错误.这可能是由于实体框架使用不正确的连接字符串引起的.检查内部异常以获取详细信息并确保连接字符串正确.”这是完整的异常链：

System.Data.ProviderIncompatibleException : An error occurred while getting provider information from the database. This can be caused by Entity Framework using an incorrect connection string. Check the inner exceptions for details and ensure that the connection string is correct.

System.Data.ProviderIncompatibleException : The provider did not return a ProviderManifestToken string.

System.InvalidOperationException : This operation requires a connection to the ‘master’ database. Unable to create a connection to the ‘master’ database because the original database connection has been opened and credentials have been removed from the connection string. Supply an unopened connection.

System.Data.SqlClient.SqlException : A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider,error: 40 – Could not open a connection to SQL Server)