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Hai,

Can anybody explain me whats the difference between Properties and normal Fields in csharp. If u show some example then it would be more better...

And i got some error here while assigning null to a integer property....
private int a;
public int A
{
    get {
        return a;
    }
    set {
        a = value;
    }
}
private int b;
public int B
{
    get { return b; }
    set { b = value; }
}

Assigning
*********
Class1 c1 = new Class1

c1.A= int.parse(tb1.text)  // Here text box is empty so getting error

c1.B=int.parse(tb2.text)   

Can anybody explain me regarding this.....

Thanks in advance...
Posted
Updated 24-Sep-10 4:27am
v2
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Solution 1

To understand how a property is different from a field, imagine you have derived a class from a Label control, to add it the capability to change the foreground color of the shown text. Your code will be similar to the following:

public class ColoredLabel : Label
{
   private Color _Foreground = Color.Black;

   ...

   public Color Foreground
   {
      get
      {
         return _Foreground;
      }
      set
      {
         _Foreground = value;
         Invalidate();
      }
   }

   ...

}


As you can see, using a property allow you to do more than simply get and/or set the value of a field.

About the error that you are getting, see the documentation of the Int32.Parse Method (String)[^]: as it could fails and throws an exception in some cases, you have to add exception-handling to your code to make it robust:

try
{
   c1.A = int.Parse(tb1.Text);
}
catch (FormatException e)
{
   // The text in the TextBox doesn't match an int
   ...
}
catch (OverflowException e)
{
   // The number in the TextBox is out of the admitted range for an int
   string text = tb1.Text;
   text.Trim();
   if (text.StartsWith("-"))
      c1.A = int.MinValue;
   else
      c1.A = int.MaxValue;
}
catch (Exception e)
{
   // Something else goes wrong
   ...
}
   
v2
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Solution 2

In your sample above private int a; is a field while public int A is a property; the property contains a setter and/or getter, and may also include validation or other supporting code. A field is merely a variable.

In your assignment statement you receive an error because null is not an integer and so cannot be assigned to c1.A. Later versions of .NET introduce the concept of nullable variables.
   
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Solution 4

Use the int.TryParse method. It returns a bool that indicates if it was a valid integer so that you don't have to rely on the try/catch mechanism (there's really no point in throwing an exception when you can otherwise easily enough verify/react to the expected results.
   
v2
Comments
Sauro Viti 24-Sep-10 11:05am
   
I'm with you! It's easier to use TryParse than handling an exception; I proposed the try/catch mechanism but only because it allow to distinguish between overflow and other failure reasons.
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Solution 3

you cannot parse empty value to int, thats why its throwing error.

use int.parse(tb1.text == string.empty? "0" : tb1.text)

make sure that if tb1.text is not empty, should return int value for parsing
   

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