Reading Empty Cells

[haroldjclements]

I have a problem with reading null value from my database. The connection works and does retrieve the data. However if there is an empty cell in the database it creates an exception �java.lang.classCastException: Specified cast is not valid�

 

while (myDataReader.Read())
{
description = myDataReader.GetString(0);
//The error is here!
custPN = System.Convert.ToString(myDataReader.GetString(2));
//custPN = myDataReader.GetString(2);
sql = "SELECT Name FROM tblSupplier WHERE SupplierID = " + myDataReader.GetInt16(1);
}	

 

I have tried to convert the output to a string, but that did not work. I think that the problem is with the .GetString() line as a blank cell is not a string. This cell is not always empty so .GetString() works fine when it's not.

 

If anyone could help me I will be eternally grateful

[haroldjclements]

ok, I have worked it out. Using the try and catch you can tell your program to just ignore that error.

 

Hope this helps someone.

Harold

[samsmithnz]

Try checking to see if the value is null before assigning it to the string. You'll find this alot quicker than catching an exception.

[haroldjclements]

Hello, I know it�s been a long time since your post but I have come across the same problem again.

 

How would you check to see if the item being dragged from the database is null?

 

If I use the �myDataReader.GetString(x)� within an �if� statement then I still get the error, so presumably I need to test the object before the conversion.

 

My question is how?

 

Thanks in advance,

Harold Clements

[haroldjclements]

Ok found it:

 

if (myDataReader.IsDBNull(5)){textBox3.set_Text("");}
else {textBox3.set_Text(myDataReader.GetString(5));}

 

Cheers,

Harold Clements