Linq错误-"NotSupportedException:用于查询运算符'Select'的不支持的重载" [英] Linq error - "NotSupportedException: Unsupported overload used for query operator 'Select'"

问题描述

我有以下Linq查询:

I have the following Linq query:

var tmp = 
    from container in Container
    join containerType in ContainerType on container.ContainerType equals containerType
    where containerType.ContainerTypeID == 2
    select new { ContainerID = container.ContainerID, TypeID = container.ContainerTypeID};

var results = tmp.Select((row, index) => new { row.ContainerID, row.TypeID, ContainerIndex = index })

按原样，这可以正常工作.如果添加以下内容，以便可以在LinqPad中查看结果，则会收到此消息标题中描述的错误:

As is, this works fine. If I add the following, so I can see the results in LinqPad, I get the error described in the title of this message:

results.Dump();

此错误不是LinqPad错误，它来自Linq，我不明白这是什么意思.

This error is not a LinqPad error, it's coming from Linq, and I don't understand what it means.

谢谢.

推荐答案

好吧，我还没有意识到Container是从LINQ to SQL数据源开始的.基本上，它无法将第二个投影转换为SQL.

Okay, I hadn't realised Container was a LINQ to SQL data source to start with. Basically it's failing to convert the second projection to SQL.

因此，您只想在.NET中执行该操作-您可以强制将其与AsEnumerable一起使用Enumerable.Select:

So, you want to do just that bit in .NET instead - you can force it to use Enumerable.Select with AsEnumerable:

var results = tmp.AsEnumerable()
                 .Select((row, index) => new { row.ContainerID, row.TypeID,
                                               ContainerIndex = index });

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