calling an overloaded method in generic method

Question

class Test
{
    public BinaryWriter Content { get; private set; }
    public Test Write<T> (T data)
    {
        Content.Write(data);
        return this;
    }
}

it won't compile.

1. The best overloaded method match for 'System.IO.BinaryWriter.Write(bool)' has some invalid arguments
2. Argument 1: cannot convert from 'T' to 'bool'

it seems like Test.Write is always trying to call BinaryWriter.Write(bool). any suggestions?

Answer 1

Overload resolution happens at compile-time, and in this case nothing is known about T, so no overload is applicable.

   class Test
    {
        public BinaryWriter Content { get; private set; }
        public Test Write<T>(T data)
        {
            Content.Write((dynamic)data);
            return this;
        }
    }

But of course it could make some problems. For example, appliction will compile fine, if you will send DateTime to the method. But, it will throw exception.

Answer 2

This is possible but not with generic constraints . You can try to use Reflection and get the appropriate overloaded version of Write method according to type of T.

Initialize your BinaryWriter with a Stream in your constructor then use Reflection like below:

class Test
{
    public BinaryWriter Content { get; private set; }

    public Test(Stream stream)
    {
        Content = new BinaryWriter(stream);
    }

    public Test Write<T>(T data)
    {

        var method = typeof (BinaryWriter).GetMethod("Write", new[] {data.GetType()});
        if (method != null)
        {
            method.Invoke(Content, new object[] { data });
        }
        // here you might want to throw an exception if method is not found

        return this;
    }
}

Here is a test program:

Test writer;
using (var fs = new FileStream("sample.txt", FileMode.Open))
{
     writer = new Test(fs);
     writer = writer.Write(232323);
     writer = writer.Write(true);
     writer = writer.Write(12);
}

using (var fs = File.Open("sample.txt", FileMode.Open))
{
    var reader = new BinaryReader(fs);
    Console.WriteLine(reader.ReadInt32());  // 232323
    Console.WriteLine(reader.ReadBoolean()); // true
    Console.WriteLine(reader.ReadByte());    // 12
}