C# Tips & Tricks #34 – “default” keyword

c#This blog post will explain what is the default keyword in C# and the usecase of the default keyword in C#.

The “Default” keyword in c# can be used in the following scenarios .

The main use of default comes in to picture when used in the generic code.

What is the use of “default” keyword in C# ?

1. To return Type’s Default Value

The Default returns the type’s default value.

For the Integer , it returns 0 , for Boolean , it returns false and for the reference types , it returns null

int valueI = default(Int32);

bool ValueB = default(Boolean);

string senthil = default(String);

MessageBox.Show(valueI.ToString()) ;// "0"

MessageBox.Show(ValueB.ToString()); // "False"

MessageBox.Show(senthil); // nothings

There is another way to get the default value via the following example.

int ValueI = new int();

Here ValueI will be 0 .


2. The keyword default is used within the switch case block to take the default value if nothing is found .

int i =0 ;

switch (i)

{

     case 1 :

               MessageBox.Show("1");

               break;

     case 2 :

               MessageBox.Show("2");

               break;

     case 3:

               MessageBox.Show("3");

               break;

     default:

               MessageBox.Show("Default");

}


3. To know , if the type is a Reference or  Value type

if (default(T) == null)
    MessageBox.Show("Reference Type");
else
    MessageBox.Show("Value Type");
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