我认为问题是由你的存根函数的返回类型引起的.

I think the problem is caused by the return type of your stub function.

您能否检查您的 FilterCustomersByRating 方法在 DbContext 中的返回类型是什么?我不认为它应该是 XMLTest.它应该类似于下面的代码:

Can you check what the return type for your FilterCustomersByRating method is in your DbContext? I don't think it should be XMLTest. It should look similar to the code below:

[EdmFunction("TestingDbEntities", "FilterCustomersByRating")]
public virtual IQueryable<FilterCustomersByRating_Result> FilterCustomersByRating(Nullable<int> rating)
{
    var ratingParameter = rating.HasValue ?
        new ObjectParameter("Rating", rating) :
        new ObjectParameter("Rating", typeof(int));

    return ((IObjectContextAdapter)this)
    .ObjectContext
    .CreateQuery<FilterCustomersByRating_Result>("[TestingEntities]
        .[FilterCustomersByRating](@Rating)", ratingParameter);
}

在这种情况下，存根函数的返回类型将是 FilterCustomersByRating_Result 类型，当您将 FilterCustomersByRating 表值函数添加到您的edmx 文件.

In this case, the return type of the stub function would be of type FilterCustomersByRating_Result which is class auto-generated when you add the FilterCustomersByRating Table-valued function to your edmx file.

CREATE FUNCTION [dbo].[FilterCustomersByRating] 
    (@Rating int) 
RETURNS TABLE
AS 
RETURN
    SELECT XMLTest.*
    FROM XMLTest
    CROSS APPLY XMLValue.nodes('//MetaData') N(C)
    where N.C.value('Rating[1]', 'int')=@Rating
GO

考虑到这一点，您的存根函数应该返回 IQueryable<FilterCustomersByRating_Result>即

With this in mind your stub function should be return IQueryable<FilterCustomersByRating_Result> i.e.

[EdmFunction("TestingDbEntities", "FilterCustomersByRating")]
public static IQueryable<FilterCustomersByRating_Result> MyXmlHelper(int rating)
{ 
    throw new NotImplementedException("You can only call this function in a LINQ query");
}

你可以如下图使用它:

var dbCustomers = (from x in _context.XMLTests
                   where MyXmlHelper(1).Any(xh => xh.XMLValue.Contains("1"))
                   select x);

请注意，虽然这会起作用，但它会返回所有 Customers.您可能需要修改 FilterCustomersByRating 函数以接受 CustomerID 和 rating.

Please note that while this will work it will return all Customers. You might need to modify the FilterCustomersByRating function to accept theCustomerID and rating.

试一试.

编辑

除了上述之外，当定义 MyXmlHelper EdmFunction，请确保FunctionName和NamespaceName的拼写正确.在我的情况下， FunctionName 是 FilterCustomersByRating 并且 NamespaceName 是 TestingEntities ，它们与自动生成的 DBContext 中的值相匹配类.

In addition to the above, when defining the MyXmlHelper EdmFunction, make sure that the spelling of the FunctionName and NamespaceName is correct. In my case, the FunctionName is FilterCustomersByRating and NamespaceName is TestingEntities which match the values in the auto-generated DBContext class.

// </auto-generated code>
public partial class TestingEntities : DbContext
{
    public TestingEntities()
        : base("name=TestingEntities")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        throw new UnintentionalCodeFirstException();
    }

    public DbSet<XMLTest> XMLTests { get; set; }

    [EdmFunction("TestingEntities", "FilterCustomersByRating")]
    public virtual IQueryable<FilterCustomersByRating_Result> FilterCustomersByRating(Nullable<int> rating)
    {
        var ratingParameter = rating.HasValue ?
            new ObjectParameter("Rating", rating) :
            new ObjectParameter("Rating", typeof(int));

        return ((IObjectContextAdapter)this)
        .ObjectContext
        .CreateQuery<FilterCustomersByRating_Result>("[TestingEntities]
            .[FilterCustomersByRating](@Rating)", ratingParameter);
    }
}