LINQ to Entities中只支持无参数构造函数和初始值设置 [英] Only parameterless constructors and initializers are supported in LINQ to Entities

问题描述

帮我理解为什么这不工作：

  Dim i =（From f In EfUtil.Db.EMAILADDRESSHISTORY _ 
其中f.EMAILADDRESS.CUSTOMERCONTACTPERSON.CUSTOMERguid = New Guid（Request.QueryString（customer））_ 
选择新建与{.guid = f.ACTIONguid，.name = f.ACTIONname}）。 ToList 
  

我收到以下错误

< blockquote>

LINQ
中仅支持无参数构造函数和初始值设置。

Altough I在这个建筑工程中发现很多例子。我缺少什么？

解决方案

您发现最有可能的示例是LINQ to Objects示例，而不是LINQ to Entities。 p>

您可以通过事先声明GUID来解决此问题：

  Dim customerGuid作为Guid = New Guid（Request.QueryString（customer））
 Dim i =（From f In EfUtil.Db.EMAILADDRESSHISTORY _ 
其中f.EMAILADDRESS.CUSTOMERCONTACTPERSON.CUSTOMERguid = customerGuid _ 
选择新建{.guid = f.ACTIONguid，.name = f.ACTIONname}）ToList 
  

选择。问题是在 Where 条件中的 New Guid（...）。

Help me understand why this isn't working:

Dim i = (From f In EfUtil.Db.EMAILADDRESSHISTORY _
                Where f.EMAILADDRESS.CUSTOMERCONTACTPERSON.CUSTOMERguid = New Guid(Request.QueryString("customer")) _
                Select New With {.guid = f.ACTIONguid, .name = f.ACTIONname}).ToList

I'm getting the following error

Only parameterless constructors and initializers are supported in LINQ to Entities.

Altough I'm finding a lot of examples where this construction works. What am I missing?

解决方案

The examples you are finding most likely are LINQ to Objects examples and not LINQ to Entities.

You can work around this by declaring the GUID beforehand:

Dim customerGuid as Guid = New Guid(Request.QueryString("customer"))
Dim i = (From f In EfUtil.Db.EMAILADDRESSHISTORY _
         Where f.EMAILADDRESS.CUSTOMERCONTACTPERSON.CUSTOMERguid = customerGuid _
         Select New With {.guid = f.ACTIONguid, .name = f.ACTIONname}).ToList

To be clear: The problem here is not your Select. The problem is the New Guid(...) in the Where condition.

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