实体框架 - 无法将 lambda 表达式转换为类型“字符串"，因为它不是委托类型 [英] Entity Framework - Cannot convert lambda expression to type 'string' because it is not a delegate type

问题描述

我在基于 C# 的代码中使用实体框架.我遇到了意想不到的怪事，正在寻求建议.

I am using Entity Framework in my C# based code. I am running into an unexpected weirdness and am looking for suggestions.

案例 1、2、3、4...项目:
RivWorks.dll
RivWorks.Service.dll
RivWorks.Alpha.dll

Case 1, 2, 3, 4... Projects:
RivWorks.dll
RivWorks.Service.dll
RivWorks.Alpha.dll

示例(所有这些工作):
RivWorks.Alpha.dll:

Samples (all of these work):
RivWorks.Alpha.dll:

public static bool EndNegotitation(long ProductID)
{
    var product = (from a in _dbFeed.AutoWithImage 
                   where a.AutoID == ProductID select a).FirstOrDefault();
...
}

RivWorks.Service.dll

public static RivWorks.Model.NegotiationAutos.AutoWithImage 
    GetProductById(long productId)
{
    var myProduct = from a in _dbFeed.AutoWithImage 
                    where a.AutoID == productId select a;

    return myProduct.FirstOrDefault();
}
public static List<RivWorks.Model.NegotiationAutos.AutoWithImage> 
    GetProductByCompany(Guid companyId)
{
    var myProduct = from a in _dbFeed.AutoWithImage 
                    where a.CompanyID == companyId select a;

    return myProduct.ToList();
}

等

案例怪异":
RivWorks.Web.Service.dll(WCF 项目)
包含与其他项目相同的引用.

Case "weirdness":
RivWorks.Web.Service.dll (WCF project)
Contains the same references as the other projects.

public NegotiateSetup GetSetup(string method, string jsonInput)
{
    ...
    long.TryParse(ProductID, out result);
    var product = (from a in _dbFeed.AutoWithImage 
                   where a.AutoID == result select a).FirstOrDefault();
    ...
}

我收到此编译时错误(在我的编辑器中突出显示了where"一词):
无法将 lambda 表达式转换为类型字符串"，因为它不是委托类型

I am getting this compile time error (the word "where" is highlighted in my editor):
Cannot convert lambda expression to type 'string' because it is not a delegate type

有什么想法会导致这种情况吗?

Any ideas what would cause this?

推荐答案

对于那些对结果感兴趣的人:
我在代码的开头缺少一个简单的 Using 语句.

For those interested in the outcome:
I was missing a simple Using statement at the head of my code.

using System.Linq;

这个问题就解决了.

这篇关于实体框架 - 无法将 lambda 表达式转换为类型“字符串"，因为它不是委托类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！