Field Initialization

C# automatically initializes class fields to default values.  The assigned default value depends on the field’s type
(integer, string, etc.)


// C# automatically sets all member variables to a safe default value.
class DefaultValues
{
  // Here are a number of fields and the corresponding defaults
  private sbyte   theSignedByte;  // = 0
  private byte    theByte;        // = 0
  private short   theShort;       // = 0
  private int     theInt;         // = 0
  private long    theLong;        // = 0
  private char    theChar;        // = 0
  private float   theFloat;       // = 0.0
  private double  theDouble;      // = 0.0
  private bool    theBool;        // = false
  private decimal theDecimal;     // = 0
  private string  theStr;         // = null
  private object  theObj;         // = null
}


You can also initialize fields in the class declaration.  This is helpful if a field should default to a value that is
different from the runtime-supplied default.  


// This technique is useful when you don’t want to use the supplied
// default values and don’t want to write the same code in each ctor.
public class Test
{
  private int myInt = 90;
  private string myStr = "My initial value";
  private Employee myEmp = new Employee();
}

     
In contrast, local variables in a method scope do not receive automatic default assignments.  You will need to set
the variable to an initial value before use, or else you will receive a compile time error.


public static void MyMethod()
{
 // Error!  myInt is not assigned an initial value before use!
 int myInt;
 myInt++;

 // OK!  myBool is assigned an initial value before use.
 bool myBool = true;
 Console.WriteLine("myBool has the value of: " + myBool);
}
Field Initialization
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C# Tutorial | C#.NET Tutorial | Field Initialization Tutorial

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