How to add my own datatype in C# program?

Like "int" refers to "Int32" class, "string" refers to "String" class. H开发者_高级运维ow to refer a datatype like "abc" to my "Abc" class?

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Your "class" is a data type.

The examples you give are the difference between CLR data type names and C# datatype names. They are aliases. C# int maps to CLR Int32 and C# string maps to CLR String.

You can create your own aliases by using "using Xyx=Abc". You must do this in each source file, so it is not that useful.

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You can add an alias like this:

using abc = MyNamespace.Abc;

But I would question why you would want to do this.

[Another poster pointed out a valid use, namely namespace type clashes, but then I would always use the fully qualified type name otherwise it might get very confusing.]

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using abc = MyNamespace.Abc;

I'm not sure what the advantage of this would be, it's usually used if you find different types with the same name.

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You're completely misunderstanding what a "data type" is. In C#, keywords like int, string, etc. are simply aliases for the corresponding types (implemented as classes/structs) already present in the CLR. For example, int has exactly the same meaning as System.Int32, which is a struct defined by the core of the .NET framework. Similarly, string simply means System.String, which is a class.

In .NET, every "data type" eventually inherits from System.Object (which is aliased as object in C#). The data types you refer to are simply pre-implemented classes and structs that inherit from System.Object; there's nothing special about them. You should realize that C# does not have special primitive types in the same way that other languages do: they're all just part of a common type hierarchy. The keywords you're used to are simply provided as a convenience.

In essence, don't worry about it. Your classes can be used as they are, and this is how they are supposed to be used.

Some reading:

• http://www.informit.com/articles/article.aspx?p=24456
• http://en.wikipedia.org/wiki/Common_Type_System
• http://msdn.microsoft.com/en-us/library/ms173104.aspx

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types like int, etc are build in types / reserved keywords. Those are defined by the compiler, so it's not possible to add your own.

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The feature you are looking for is probably something you are used to from C++. There is no equivalent concept in C#. All you have are the builtin data type. The only thing you can declare is you own class or struct, but not datatype.

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there is no way to define custom datatypes in c# i have the same problem and i searched for the solution with no success in my case i need to define a datatype for unmanaged types like MarshalAs(UnmanagedType.LPWStr)]

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Q: Why would someone want to do this?

A: To produce self documented code.

using InternalLoggerName = System.String;
using ExternalLoggerName = System.String;

namespace LoggingUtils
{
  public static class LoggerPool
  {
    private static readonly 
       ConcurrentDictionary
         <
             ExternalLoggerName
           , InternalLoggerName
        >                          LoggerNameMappings 
      = new ConcurrentDictionary<ExternalLoggerName, InternalLoggerName>();


    public static ILog GetLogger(string loggerName)
    {
      // and you don't have to expose the aliases to the outside world
    }
  }
}