Support for Named and Optional Parameters

Support for Optional parameters, default values and named parameters are new interesting features added to C# 4.0. You now no longer need to bother about your parameters in method calls - they have now been made much simpler. Consider the following method:

public static int AddValues(int x = 5, int y = 10)
{
  return (x + y);
}

You can now call this method AddValues() as simply as the following call shows you to:

int myValue = AddValues(); //The myValue integer variable would now have a value of 15.

Refer to the code snippet above. As you can see, the default values assigned to the parameters in the AddValues() method are 5 and 10. So, even if you don't pass any value when invoking the method, these values would be considered.

Enhanced COM Interop Features

C# 4.0 now allows you to have better flexibility in writing COM interoperable code - it is now much easier to call COM objects from your .NET code. Refer to the following code sample that shows how you can open a Microsoft Word Document in C#.

using Word = Microsoft.Office.Interop.Word;

namespace PCQ
{
    class Program
    {
        static void Main(string[] args)
        {
            Word.Application wordApplication = new Word.Application() { Visible = true };
            object missingValue = System.Reflection.Missing.Value;
            object readOnlyValue = true;
            object fileName = @"E:\\PCQ.docx";
            wordApplication.Documents.Open(ref fileName, ref missingValue, ref readOnlyValue,
                ref missingValue, ref missingValue, ref missingValue, ref missingValue, ref missingValue, ref missingValue,
                ref missingValue, ref missingValue, ref missingValue, ref missingValue, ref missingValue,ref missingValue);
        }
    }
}