Dapper 查询映射的 Dynamic Func<>

Question

我正在尝试为Dapper 动态生成和执行 sql，目的是简单地传入一个类型，然后动态生成和执行 sql。

示例类：

public class User
{
    [Key]
    public int UserId { get; set; }
    public Address Address { get; set; }
}
public class Address
{
    [Key]
    public int UserId { get; set; }
    public string PostCode { get; set; }
}

将有效地运行以下内容：

// sql: "SELECT User.UserId, Address.UserId, Address.PostCode FROM User LEFT JOIN Address ON Address.User = User.UserId"... // auto generated from 'User' type including join to 'Address';

connection.Query<User, Address, User>(sql, /*** map argument needs to be dynamic Func<> ***/);

因此，鉴于这些类型 User 和 Address 仅在运行时已知，我如何生成适当的委托 Func<User, Address, User> 以传递给 map 参数？

Func<User, Address, User> map = (u, a) => {
    u.Address = a;
    return u;
}

我看到使用反射创建Func<> 的examples 假设类型是已知的，在我的情况下它们不是，因此类型参数会有所不同（Func / Func / Func 等）。

任何帮助表示赞赏。我将继续研究使用表达式的示例，看看是否有任何问题。

Answer 1

这是我得到的最接近的结果。我试图克隆 Dapper 存储库以深入了解 Query() 方法的工作原理，但我使用的是旧版本的 Visual Studio。

public static class DynamicFuncHelper
{
    public static Delegate CreateFunc(Type type1, Type type2)
    {
        Type funcType = typeof(Func<,,>).MakeGenericType(type1, type2, type1);
        MethodInfo method =
            typeof(DynamicFuncHelper<,>)
            .MakeGenericType(type1, type2)
            .GetMethod("SetAddressProperty",
                BindingFlags.Public | BindingFlags.Static
            );
        return Delegate.CreateDelegate(funcType, method);
    }
}

public static class DynamicFuncHelper<T,U> 
    where T : class 
    where U : class
{
    public static T SetAddressProperty(T obj1, U obj2)
    {
        obj1.GetType().InvokeMember("Address",
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty,
            Type.DefaultBinder, obj1, new[] { obj2 });
        return obj1;
    }
}

通过了这个单元测试

[TestClass]
public class DynamicFuncTest
{
    [TestMethod]
    public void TestDynamicMapper()
    {
        var actualUser = new User { UserId = 1 };
        var actualAddress = new Address { PostCode = "12345", UserId = 1 };
        var testSetAddress = DynamicFuncHelper.CreateFunc(typeof(User), typeof(Address));
        var delegateResult = testSetAddress.DynamicInvoke(actualUser, actualAddress);
        Assert.AreEqual(actualUser, delegateResult, "Delegate result was not actualUser");
        Assert.AreEqual(actualAddress, actualUser.Address, "User address was not expected address");
    }
}