C# cast object type

Question

How can I cast object type to different type?

public T Get<T>(T t)
{
    if (t is TypeA)
    {
        TypeA a = (TypeA)t; //error
    }
}

Answer 1

试试这样：

TypeA a = (TypeA)(object)t;

Answer 2

One way would be to use as

public T Get<T>(T t)
{
    if(t is TypeA) {
        TypeA a = t as TypeA;
    }
}

The other would be to use Convert

public T Get<T>(T t)
{
    if(t is TypeA) {
        TypeA a = (TypeA) Convert.ChangeType(t, typeof(TypeA));
    }
}

Answer 3

https://dotnetfiddle.net/7tb2Fl

I couldn't get an error here. It will cast fine

using System;

public class Program
{
    public class TypeA
    {
        public int Id;
    }

    public class TypeB : TypeA
    {
        public int name;
    }

    public static void Main()
    {
        var t = new TypeB{Id = 1, name = 15};
        if (t is TypeA)
        {
            TypeA a = (TypeA)t;// no error
            Console.WriteLine(a.Id); // no error
        }
    }
}

Answer 4

//Just thought of it and not tested:

public T ConvertType<T>(Object obj)
{
    if (obj is T)
        return (T)Convert.ChangeType(obj, typeof(T));
    return default(T);
}