How can I call default (T) with type?

Question

In C #, I can use default(T)to get the default value for a type. I need to get the default type at runtime from System.Type. How can i do this?

eg. Something like this (which doesn't work)

var type = typeof(int);
var defaultValue = default(type);

Answer 1

For a return reference type nullfor a value type, you can try to use Activator.CreateInstanceor call the default constructor for the type.

public static object Default(Type type)
{
   if(type.IsValueType)
   {
      return Activator.CreateInstance(type);
   }

   return null;
}

Answer 2

If you are trying to build an expression tree, use Expression.Default:

Expression expression = Expression.Default(type);

Another way you could do this quite easily would be:

object defaultValue = Array.CreateInstance(type, 1).GetValue(0);

, :) , NULL, .

, (void ), , :)

Answer 3

, 2 :

• : null

• : , Activator.CreateInstance

  public static object GetDefaultValue(Type type)
  {
      if (type.IsValueType)
      {
          return Activator.CreateInstance(type);
      }
      else
      {
          return null;
      }
  }
  

FormatterServices.GetUninitializedObject Activator.CreateInstance, , .