.net - Convert DateTimeOffset to Datetime dynamically using C# IL.Emit

I am trying to convert DatetimeOffset to DateTime on runtime using c# DynamicMethod and GetILGenerator. I can able to convert from DateTimeOffset?-> DateTime, DateTimeOffset -> DateTime ..etc except DateTimeOffset? to DateTime?. The converted UTC value is not used while creating the `DateTime?' object. Not Sure what is wrong in below

using System;
using System.Reflection;
using System.Reflection.Emit;

public class Program
{
    public static Func<TInputValue, TOutputValue> GenerateConverter<TInputValue, TOutputValue>()
    {
        var inputType = typeof(TInputValue);
        var outputType = typeof(TOutputValue);

        // Create a dynamic method with a single parameter (DateTimeOffset)
        var method = new DynamicMethod(
            "ConvertDateTimeOffsetToUtcDateTime",
            outputType,
            new[] { inputType });

        var inputIsNullable = inputType.IsGenericType && inputType.GetGenericTypeDefinition() == typeof(Nullable<>);
        var outputIsNullable = outputType.IsGenericType && outputType.GetGenericTypeDefinition() == typeof(Nullable<>);

        var il = method.GetILGenerator();

        // Get methods and properties needed for DateTimeOffset and DateTime conversion
        var getValueMethod = typeof(DateTimeOffset?).GetProperty("Value").GetGetMethod();
        var utctimeMethod = typeof(DateTimeOffset).GetProperty("UtcDateTime").GetGetMethod();
        var hasValueMethod = typeof(DateTimeOffset?).GetProperty("HasValue").GetGetMethod();

        Label returnNullLabel = il.DefineLabel();
        Label continueLabel = il.DefineLabel();

        // Step 1: Check if the input value is null (for nullable DateTimeOffset?)
        if (inputIsNullable)
        {
            // Load the argument (DateTimeOffset?)
            il.Emit(OpCodes.Ldarga_S, 0);
            // Check if the DateTimeOffset? has a value (not null)
            il.Emit(OpCodes.Call, hasValueMethod);
            il.Emit(OpCodes.Brfalse_S, returnNullLabel); // If null, jump to returnNullLabel

            // Load the value (unbox DateTimeOffset)
            il.Emit(OpCodes.Ldarga_S, 0);
            il.Emit(OpCodes.Call, getValueMethod);
        }
        else
        {
            il.Emit(OpCodes.Ldarg_0); // Load the non-nullable DateTimeOffset
        }

        // Step 2: Get the UtcDateTime (this is the DateTime value in UTC)
        il.Emit(OpCodes.Call, utctimeMethod);

        // Step 3: If output is nullable (DateTime?), box the DateTime into Nullable<DateTime>
        if (outputIsNullable)
        {
            // Use the Nullable<DateTime> constructor that takes a DateTime
            var ctor = outputType.GetConstructor(new[] { typeof(DateTime) });
            il.Emit(OpCodes.Newobj, ctor); // Box the DateTime into Nullable<DateTime>
        }

        il.Emit(OpCodes.Br_S, continueLabel);

        il.MarkLabel(returnNullLabel);
        // If the input value is null, return null for Nullable<DateTime>
        if (outputIsNullable)
        {
            il.Emit(OpCodes.Ldnull); // Return null if the output is nullable
        }
        else
        {
            // If output is not nullable, throw an InvalidOperationException
            il.Emit(OpCodes.Newobj, typeof(InvalidOperationException).GetConstructor(Type.EmptyTypes));
            il.Emit(OpCodes.Throw);
        }

        il.MarkLabel(continueLabel);
        il.Emit(OpCodes.Ret); // Return the result

        // Create the delegate for the dynamic method
        return (Func<TInputValue, TOutputValue>)method.CreateDelegate(typeof(Func<TInputValue, TOutputValue>));
    }



    //public static Func<TInputValue, TOutputValue> GenerateConverter<TInputValue, TOutputValue>()
    //{

    //  var inputType = typeof(TInputValue);
    //  var outputType = typeof(TOutputValue);


    //  // Create a dynamic method with a single parameter (DateTimeOffset)
    //  var method = new DynamicMethod(
    //      "ConvertDateTimeOffsetToUtcDateTime",
    //      outputType,
    //      new[] { inputType });

    //  var inputIsNullable = inputType.IsGenericType && inputType.GetGenericTypeDefinition() == typeof(Nullable<>);
    //  var outputIsNullable = outputType.IsGenericType && outputType.GetGenericTypeDefinition() == typeof(Nullable<>);

    //  var il = method.GetILGenerator();

    //  var getValueMethod = typeof(DateTimeOffset?).GetProperty("Value").GetGetMethod();
    //  var toUniversalTimeMethod = typeof(DateTimeOffset).GetMethod("ToUniversalTime", Type.EmptyTypes);
    //  var getDateTimeMethod = typeof(DateTimeOffset).GetProperty("DateTime").GetGetMethod();
    //  var utctimeMethod = typeof(DateTimeOffset).GetProperty("UtcDateTime").GetGetMethod();



    //  var hasValueMethod = typeof(DateTimeOffset?).GetProperty("HasValue").GetGetMethod();
    //  Label returnNullLabel = il.DefineLabel();
    //  Label continueLabel = il.DefineLabel();

    //  if (inputIsNullable)
    //  {
    //      il.Emit(OpCodes.Ldarga_S, 0);
    //      il.Emit(OpCodes.Call, hasValueMethod);
    //      il.Emit(OpCodes.Brfalse_S, returnNullLabel);
    //      il.Emit(OpCodes.Ldarga_S, 0);
    //      il.Emit(OpCodes.Call, getValueMethod);

    //  }
    //  else
    //  {
    //      il.Emit(OpCodes.Ldarg_0);
    //  }


    //  il.Emit(OpCodes.Call, utctimeMethod);

    //  if (outputIsNullable)
    //  {
    //      var ctor = outputType.GetConstructor(new[] { typeof(DateTime) });
    //      il.Emit(OpCodes.Newobj, ctor);
    //  }

    //  il.Emit(OpCodes.Br_S, continueLabel);


    //  il.MarkLabel(returnNullLabel);
    //  if (outputIsNullable)
    //  {
    //      il.Emit(OpCodes.Ldnull);

    //  }
    //  else
    //  {
    //      // Throw exception for non-nullable output
    //      il.Emit(OpCodes.Newobj, typeof(InvalidOperationException).GetConstructor(Type.EmptyTypes));
    //      il.Emit(OpCodes.Throw);
    //  }

    //  il.MarkLabel(continueLabel);
    //  il.Emit(OpCodes.Ret);

    //  // Create the delegate for the dynamic method
    //  return (Func<TInputValue, TOutputValue>)method.CreateDelegate(typeof(Func<TInputValue, TOutputValue>));
    //}


    public static void Main()
    {
        // Generate the IL-based converter
        //var converter = GenerateConverter<DateTimeOffset, DateTime>();

        //// Test conversion
        //DateTimeOffset dto = DateTimeOffset.Now;

        //var result1 = converter(dto);


        //var converter2 = GenerateConverter<DateTimeOffset?, DateTime>();

        //// Test conversion
        //DateTimeOffset? data2 = DateTimeOffset.Now;

        //var result2 = converter2(data2);

        //var converter3 = GenerateConverter<DateTimeOffset, DateTime?>();

        //// Test conversion
        //DateTimeOffset data3 = DateTimeOffset.Now;

        //var result3 = converter3(data3);

        var converter3 = GenerateConverter<DateTimeOffset?, DateTime?>();

        // Test conversion
        DateTimeOffset data3 = DateTimeOffset.Now;

        var result3 = converter3(data3);

    }
}

I am trying to convert DatetimeOffset to DateTime on runtime using c# DynamicMethod and GetILGenerator. I can able to convert from DateTimeOffset?-> DateTime, DateTimeOffset -> DateTime ..etc except DateTimeOffset? to DateTime?. The converted UTC value is not used while creating the `DateTime?' object. Not Sure what is wrong in below

using System;
using System.Reflection;
using System.Reflection.Emit;

public class Program
{
    public static Func<TInputValue, TOutputValue> GenerateConverter<TInputValue, TOutputValue>()
    {
        var inputType = typeof(TInputValue);
        var outputType = typeof(TOutputValue);

        // Create a dynamic method with a single parameter (DateTimeOffset)
        var method = new DynamicMethod(
            "ConvertDateTimeOffsetToUtcDateTime",
            outputType,
            new[] { inputType });

        var inputIsNullable = inputType.IsGenericType && inputType.GetGenericTypeDefinition() == typeof(Nullable<>);
        var outputIsNullable = outputType.IsGenericType && outputType.GetGenericTypeDefinition() == typeof(Nullable<>);

        var il = method.GetILGenerator();

        // Get methods and properties needed for DateTimeOffset and DateTime conversion
        var getValueMethod = typeof(DateTimeOffset?).GetProperty("Value").GetGetMethod();
        var utctimeMethod = typeof(DateTimeOffset).GetProperty("UtcDateTime").GetGetMethod();
        var hasValueMethod = typeof(DateTimeOffset?).GetProperty("HasValue").GetGetMethod();

        Label returnNullLabel = il.DefineLabel();
        Label continueLabel = il.DefineLabel();

        // Step 1: Check if the input value is null (for nullable DateTimeOffset?)
        if (inputIsNullable)
        {
            // Load the argument (DateTimeOffset?)
            il.Emit(OpCodes.Ldarga_S, 0);
            // Check if the DateTimeOffset? has a value (not null)
            il.Emit(OpCodes.Call, hasValueMethod);
            il.Emit(OpCodes.Brfalse_S, returnNullLabel); // If null, jump to returnNullLabel

            // Load the value (unbox DateTimeOffset)
            il.Emit(OpCodes.Ldarga_S, 0);
            il.Emit(OpCodes.Call, getValueMethod);
        }
        else
        {
            il.Emit(OpCodes.Ldarg_0); // Load the non-nullable DateTimeOffset
        }

        // Step 2: Get the UtcDateTime (this is the DateTime value in UTC)
        il.Emit(OpCodes.Call, utctimeMethod);

        // Step 3: If output is nullable (DateTime?), box the DateTime into Nullable<DateTime>
        if (outputIsNullable)
        {
            // Use the Nullable<DateTime> constructor that takes a DateTime
            var ctor = outputType.GetConstructor(new[] { typeof(DateTime) });
            il.Emit(OpCodes.Newobj, ctor); // Box the DateTime into Nullable<DateTime>
        }

        il.Emit(OpCodes.Br_S, continueLabel);

        il.MarkLabel(returnNullLabel);
        // If the input value is null, return null for Nullable<DateTime>
        if (outputIsNullable)
        {
            il.Emit(OpCodes.Ldnull); // Return null if the output is nullable
        }
        else
        {
            // If output is not nullable, throw an InvalidOperationException
            il.Emit(OpCodes.Newobj, typeof(InvalidOperationException).GetConstructor(Type.EmptyTypes));
            il.Emit(OpCodes.Throw);
        }

        il.MarkLabel(continueLabel);
        il.Emit(OpCodes.Ret); // Return the result

        // Create the delegate for the dynamic method
        return (Func<TInputValue, TOutputValue>)method.CreateDelegate(typeof(Func<TInputValue, TOutputValue>));
    }



    //public static Func<TInputValue, TOutputValue> GenerateConverter<TInputValue, TOutputValue>()
    //{

    //  var inputType = typeof(TInputValue);
    //  var outputType = typeof(TOutputValue);


    //  // Create a dynamic method with a single parameter (DateTimeOffset)
    //  var method = new DynamicMethod(
    //      "ConvertDateTimeOffsetToUtcDateTime",
    //      outputType,
    //      new[] { inputType });

    //  var inputIsNullable = inputType.IsGenericType && inputType.GetGenericTypeDefinition() == typeof(Nullable<>);
    //  var outputIsNullable = outputType.IsGenericType && outputType.GetGenericTypeDefinition() == typeof(Nullable<>);

    //  var il = method.GetILGenerator();

    //  var getValueMethod = typeof(DateTimeOffset?).GetProperty("Value").GetGetMethod();
    //  var toUniversalTimeMethod = typeof(DateTimeOffset).GetMethod("ToUniversalTime", Type.EmptyTypes);
    //  var getDateTimeMethod = typeof(DateTimeOffset).GetProperty("DateTime").GetGetMethod();
    //  var utctimeMethod = typeof(DateTimeOffset).GetProperty("UtcDateTime").GetGetMethod();



    //  var hasValueMethod = typeof(DateTimeOffset?).GetProperty("HasValue").GetGetMethod();
    //  Label returnNullLabel = il.DefineLabel();
    //  Label continueLabel = il.DefineLabel();

    //  if (inputIsNullable)
    //  {
    //      il.Emit(OpCodes.Ldarga_S, 0);
    //      il.Emit(OpCodes.Call, hasValueMethod);
    //      il.Emit(OpCodes.Brfalse_S, returnNullLabel);
    //      il.Emit(OpCodes.Ldarga_S, 0);
    //      il.Emit(OpCodes.Call, getValueMethod);

    //  }
    //  else
    //  {
    //      il.Emit(OpCodes.Ldarg_0);
    //  }


    //  il.Emit(OpCodes.Call, utctimeMethod);

    //  if (outputIsNullable)
    //  {
    //      var ctor = outputType.GetConstructor(new[] { typeof(DateTime) });
    //      il.Emit(OpCodes.Newobj, ctor);
    //  }

    //  il.Emit(OpCodes.Br_S, continueLabel);


    //  il.MarkLabel(returnNullLabel);
    //  if (outputIsNullable)
    //  {
    //      il.Emit(OpCodes.Ldnull);

    //  }
    //  else
    //  {
    //      // Throw exception for non-nullable output
    //      il.Emit(OpCodes.Newobj, typeof(InvalidOperationException).GetConstructor(Type.EmptyTypes));
    //      il.Emit(OpCodes.Throw);
    //  }

    //  il.MarkLabel(continueLabel);
    //  il.Emit(OpCodes.Ret);

    //  // Create the delegate for the dynamic method
    //  return (Func<TInputValue, TOutputValue>)method.CreateDelegate(typeof(Func<TInputValue, TOutputValue>));
    //}


    public static void Main()
    {
        // Generate the IL-based converter
        //var converter = GenerateConverter<DateTimeOffset, DateTime>();

        //// Test conversion
        //DateTimeOffset dto = DateTimeOffset.Now;

        //var result1 = converter(dto);


        //var converter2 = GenerateConverter<DateTimeOffset?, DateTime>();

        //// Test conversion
        //DateTimeOffset? data2 = DateTimeOffset.Now;

        //var result2 = converter2(data2);

        //var converter3 = GenerateConverter<DateTimeOffset, DateTime?>();

        //// Test conversion
        //DateTimeOffset data3 = DateTimeOffset.Now;

        //var result3 = converter3(data3);

        var converter3 = GenerateConverter<DateTimeOffset?, DateTime?>();

        // Test conversion
        DateTimeOffset data3 = DateTimeOffset.Now;

        var result3 = converter3(data3);

    }
}

Share Improve this question asked Nov 19, 2024 at 4:20 Max_dev 5088 silver badges26 bronze badges

Well, not sure about the correctness of the emitted code you're generating, but the exception is thrown in the line il.Emit(OpCodes.Ret); // Return the result. – Matt Commented Nov 19, 2024 at 7:13

Add a comment |

1 Answer 1

Sorted by: Reset to default 1

You have two issues here, both of which you would have realised if you would have compared your generated IL to what you get from compiling it with C# (eg using https://sharplab.io).

        if (inputIsNullable)
        {
            // Load the argument (DateTimeOffset?)
            il.Emit(OpCodes.Ldarga_S, 0);
            // Check if the DateTimeOffset? has a value (not null)
            il.Emit(OpCodes.Call, hasValueMethod);
            il.Emit(OpCodes.Brfalse_S, returnNullLabel); // If null, jump to returnNullLabel

            // Load the value (unbox DateTimeOffset)
            il.Emit(OpCodes.Ldarga_S, 0);
            il.Emit(OpCodes.Call, getValueMethod);
        }
        else
        {
            il.Emit(OpCodes.Ldarg_0); // Load the non-nullable DateTimeOffset
        }

This is incorrect. If you have a valuetype on the stack, you cannot pass directly as the this to an instance method. You need to load its ref, and in the case of the nullable you need to store the Value in a local.

        il.Emit(OpCodes.Ldarga_S, (byte)0); // Load the address
        if (inputIsNullable)
        {
            // Check if the DateTimeOffset? has a value (not null)
            il.Emit(OpCodes.Call, hasValueMethod);
            il.Emit(OpCodes.Brfalse_S, returnNullLabel); // If null, jump to returnNullLabel

            // Load the value (unbox DateTimeOffset)
            il.Emit(OpCodes.Ldarga_S, 0);
            il.Emit(OpCodes.Call, getValueMethod);
            var loc = il.DeclareLocal(typeof(DateTimeOffset));
            il.Emit(OpCodes.Stloc_S, (byte)loc.LocalIndex);
            il.Emit(OpCodes.Ldloca_S, (byte)loc.LocalIndex);
        }

        if (outputIsNullable)
        {
            il.Emit(OpCodes.Ldnull); // Return null if the output is nullable
        }

This is incorrect. To create an empty nullable, you can't use ldnull which is only for object references. You need to create an empty struct using a local and initobj.

        if (outputIsNullable)
        {
            var loc = il.DeclareLocal(outputType);
            il.Emit(OpCodes.Ldloca_S, (byte)loc.LocalIndex);
            il.Emit(OpCodes.Initobj, outputType);
            il.Emit(OpCodes.Ldloc_S, (byte)loc.LocalIndex); // Return null if the output is nullable
        }

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