c# - 将 Enum.GetName(...) 合并到 Linq 查询中

Question

我有枚举:

public enum CmdType {
    [Display(Name = "abc")]
    AbcEnumIdentifier = 0,

    [Display(Name = "xyz")]
    XyzEnumIdentifier = 1,
    ...
}

我想将每个枚举的名称获取到我的查询中，但即使使用 .WithTranslations() 我也会收到此错误:

LINQ to Entities does not recognize the method 'System.String GetName(System.Type, System.Object)' method, and this method cannot be translated into a store expression.

查询:

var joinedRecord =
    (
        from m in mTable
        join b in bTable on m.Id equals b.aRefId
        select new {
            aId = a.Id,
            aAttrib1 = a.Attrib1
            ...
            bCmdType = Enum.GetName(typeof(CmdType), b.CmdType)
        }
    ).WithTranslations();

如何在查询中使用 Enum.GetName(...) 返回生成的值？

Answer 1

LINQ to entities 尝试将您的查询转换为 SQL 但未能成功，因为在 SQL 中没有等效的 Enum.GetName 方法。

您需要具体化查询结果并将枚举值转换为它们在内存中的名称。

var joinedRecords = (
    from m in mTable
        join b in bTable on m.Id equals b.aRefId
        select new {
            aId = a.Id,
            aAttrib1 = a.Attrib1
            ...
            bCmdType = b.CmdType
        }
).AsEnumerable() //Executes the query, further you have simple CLR objects
.Select(o => new {
    aId = o.Id,
    aAttrib1 = o.Attrib1
    ...
    bCmdTypeName = Enum.GetName(typeof(CmdType), o.CmdType)
});