Wednesday, June 6, 2007

Using Generics for dynamic return type and validation.

[This was originally posted at]

Generics are a .Net 2.0 feature that essentially let you abstract out type. You can learn a lot about generics on MSDN.

One problem that generics can solve is how to have a method dynamically return a given type. For example, in the snippet below, the method GetData returns different types depending on what you pass in - either a double or an Int32. This is useful for creating a generalized method to parse out (and potentially validate) data. Note that the consumer of the GetData method need not deal with conversion - it receives a strongly typed value.

While this is just a trivial snippet, it's a nice demo of one of the features of generics.

    public void DemoGenerics()
      int i = GetData("123");
      double d = GetData("456");

      Assert.AreEqual(Convert.ToInt32(123), i);
      Assert.AreEqual(Convert.ToDouble(456), d);


    public static T GetData(string strData)
      string strType = typeof(T).Name;

      switch (strType)
        case "Int32":
          return (T)(object)Convert.ToInt32(strData);
        case "Double":
          return (T)(object)Convert.ToDouble(strData);
          throw new Exception("Type not supported");


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