EF6 是否仍支持模型定义的函数？

Question

此处讨论模型定义的函数：

• https://msdn.microsoft.com/en-us/library/vstudio/dd456857(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/dd456812.aspx
• Entity Framework 6 Code First function mapping
• http://www.c-sharpcorner.com/UploadFile/ff2f08/model-defined-function/

EF6.1.2 是否支持这些？

我正在逐步浏览 Edm/DbModel 的内容，但我终其一生都无法确定应该解析 csdl 中的 元素的位置，因为它没有进入 EdmModel (EdmModel .AddItem(EdmFunction) 没有被调用）

ExpressionConverter.FindFunction 在 EdmModel._functions 中查找，并且 _functions 仅由 EdmModel.AddItem(EdmFunction) 添加，并且仅由扩展方法 EdmModelExtensions.AddFunction() 调用，我在 EntityFramework 源代码中找不到任何地方调用该函数。我一定错过了一些简单的东西......

更多：我放弃了在 edmx 中定义函数，现在我正在以编程方式创建我的 EdmFunction 并将其添加到自定义 IConceptualModelConvention.Apply() 方法中：

    class CustomFunctionConvention : IConceptualModelConvention<EdmModel>
    {
        public void Apply(EdmModel item, DbModel model)
        {
            var functionPayload = new EdmFunctionPayload () {
                CommandText = "CAST (strValue AS int)",
                Parameters = new [] {
                    FunctionParameter.Create("strValue", PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.String).GetEdmPrimitiveType(), ParameterMode.In),
                },
                ReturnParameters = new [] {
                    FunctionParameter.Create("ReturnValue", PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Int32).GetEdmPrimitiveType(), ParameterMode.ReturnValue),
                },
                IsComposable = true,
            };

            var function = EdmFunction.Create("ParseInt", "MyNamespace", DataSpace.CSpace, functionPayload, null);
            model.ConceptualModel.AddItem(function);
        }
    }

但现在我在 EdmItemCollection.LoadItems() 中遇到了一堆架构错误：

Schema specified is not valid. Errors:
(0,0) : error 0005: The 'Aggregate' attribute is not allowed.
(0,0) : error 0005: The 'BuiltIn' attribute is not allowed.
(0,0) : error 0005: The 'NiladicFunction' attribute is not allowed.
(0,0) : error 0005: The 'IsComposable' attribute is not allowed.
(0,0) : error 0005: The 'ParameterTypeSemantics' attribute is not allowed.
(0,0) : error 0005: The 'Schema' attribute is not allowed.
(0,0) : error 0005: The 'Mode' attribute is not allowed.

Answer 1

看来，模型定义的函数首先可用于代码。这是您的 ParseInt 示例的版本：

namespace EfTestModelFunctions
{
    public class CustomFunctionConvention : IConceptualModelConvention<EdmModel>
    {
        public void Apply(EdmModel item, DbModel model)
        {
            var functionParseInt = new EdmFunctionPayload()
            {
                CommandText = String.Format("CAST(strValue AS {0})", PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Int32)),
                Parameters = new[] {
                    FunctionParameter.Create("strValue", PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.String), ParameterMode.In),
                },

                ReturnParameters = new[] {
                    FunctionParameter.Create("ReturnValue", PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Int32), ParameterMode.ReturnValue),
                },
                IsComposable = true
            };

            var function = EdmFunction.Create("ParseInt", model.ConceptualModel.EntityTypes.First().NamespaceName, DataSpace.CSpace, functionParseInt, null);
            model.ConceptualModel.AddItem(function);
        }
    }

    public class RootDataContext : DbContext
    {
        public RootDataContext()
            : base("Data Source=******")
        {
            Database.SetInitializer(new NullDatabaseInitializer<RootDataContext>());
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Conventions.Add<CustomFunctionConvention>();
        }

        public DbSet<RootEntity> Roots { get; set; }

        // declare the function with the Context's NameSpace
        [DbFunction("EfTestModelFunctions", "ParseInt")]
        public static int ParseInt(string value)
        {
            throw new NotImplementedException();
        }
    }
}

然后使用：

var query = ctx.Roots.Where(r => RootDataContext.ParseInt(r.StringProperty)==123);

此外，涉及数据库迁移/初始化时似乎存在问题。看 UpForGrabs: Unblock creation of model defined functions in model conventions