as,in and reference types error msg.....

raykaash · January 7th, 2008, 07:44 AM

hi....

i am using a method like this....

public static double setDefaultDoubleValue(string txtval)
{
double dtxtval = txtval as double;
return (dtxtval is double ? dtxtval : 0.00);
}

on compiling i m getiing the error message like "use reference types rather than value type"...i tried....

System.Double in place of double bt the prob is same....

can anyone help me clearing this thing....
thnx in advance...

samjudson · January 7th, 2008, 07:53 AM

System.Double is a value type, and cannot be null (i.e. double d = null; is not valid).

The "as" keyword is used to try to store an object from one reference type to another. It returns null if the object is not of the correct type.
The "is" keyword returns true if the above transfer would work.

What you probably want to use is Double.TryParse(object, ref double);

public static double setDefaultDoubleValue(string textValue)
{
double d;
return double.TryParse(textValue, ref d) ? d : 0.00;
}

/- Sam Judson : Wrox Technical Editor -/

raykaash · January 8th, 2008, 07:14 AM

Quote:

quote:Originally posted by samjudson
System.Double is a value type, and cannot be null (i.e. double d = null; is not valid).

The "as" keyword is used to try to store an object from one reference type to another. It returns null if the object is not of the correct type.
The "is" keyword returns true if the above transfer would work.

What you probably want to use is Double.TryParse(object, ref double);

public static double setDefaultDoubleValue(string textValue)
{
double d;
return double.TryParse(textValue, ref d) ? d : 0.00;
}

/- Sam Judson : Wrox Technical Editor -/

coool.....
thanks for the support...