在实体框架中映射/使用内置的MySQL函数

Question

Quite a simple question, I hope: I want to use built-in MySQL functions just as YEARWEEK or INSERT in Entity Framework 6 (similar to the System.Data.Entity.DbFunctions namespace). Is there a way to add a mapping to those functions?

I already tried to add them via the edmx file, but that didn't work quite right.

<!-- edmx:ConceptualModels -->
<Function Name="YearWeek" ReturnType="String">
    <Parameter Name="date" Type="DateTime" />
    <DefiningExpression>
        YEARWEEK(date, 3)
    </DefiningExpression>
</Function>

<!-- edmx:StorageModels -->
<Function Name="YEARWEEK" IsComposable="true" ReturnType="varchar" BuiltIn="true" Aggregate="false" NiladicFunction="false" ParameterTypeSemantics="AllowImplicitConversion">
    <Parameter Name="date" Type="datetime" Mode="In" />
    <Parameter Name="mode" Type="int" Mode="In" />
</Function>

And in my c# code:

[System.Data.Entity.DbFunction("otrsModel", "YearWeek")]
public static string YearWeek(DateTime date) {
    throw new NotSupportedException("Direct calls are not supported.");
}

This, right now, throws me a System.Data.Entity.Core.EntityCommandCompilationException . The inner exception is: "'YEARWEEK' cannot be resolved into a valid type or function."

However, calling the following code on that same database works just fine:

var week = db.Database.SqlQuery<dynamic>("SELECT INSERT(YEARWEEK(create_time, 3), 5, 0, '/'), ticket.* AS a FROM ticket").ToList();

Any idea what's wrong here?

Answer 1

I finally solved the problem, and the solution is quite simple: Adding a definition to edmx:ConceptualModels is unnecessary. You just have to add the edmx:StorageModels definition and call it correctly. Here's my modified code with exemplary implementations of MySQL's built-in functions INSERT and YEARWEEK :

<!-- edmx:StorageModels -->
<Function Name="YEARWEEK" IsComposable="true" ReturnType="varchar" BuiltIn="true" Aggregate="false" NiladicFunction="false" ParameterTypeSemantics="AllowImplicitConversion">
  <Parameter Name="date" Type="datetime" Mode="In" />
  <Parameter Name="mode" Type="int" Mode="In" />
</Function>
<Function Name="INSERT" IsComposable="true" ReturnType="varchar" BuiltIn="true" Aggregate="false" NiladicFunction="false" ParameterTypeSemantics="AllowImplicitConversion">
  <Parameter Name="str" Type="varchar" Mode="In" />
  <Parameter Name="position" Type="int" Mode="In" />
  <Parameter Name="number" Type="int" Mode="In" />
  <Parameter Name="substr" Type="varchar" Mode="In" />
</Function>

And the corresponding c# code:

namespace MySQL_3 {
    class Program {
        static void Main(string[] args) {
            var db = new myEntities();

            var test = db.ticket.Select(t => t.change_time.YearWeek(3).Insert(5, 0, "/"));

            var test2 = test.ToList();

            Console.Read();
        }
    }

    public static class BuiltInFunctions {

        [DbFunction("myModel.Store", "YEARWEEK")]
        public static string YearWeek(this DateTime date, Int32 mode) => throw new NotSupportedException("Direct calls are not supported.");

        [DbFunction("myModel.Store", "INSERT")]
        public static string Insert(this string str, int position, int number, string substr) => throw new NotSupportedException("Direct calls are not supported.");
    }
}