if((string)row["ProductID"].ToString() == txtBarcode.Text)
I want to search a row if the value of the txtbox is the same as my datatable but i have an error.. it says that Possible unintended reference comparison; to get a value comparison, cast the left hand side to string. i just use .ToString() and Convert.ToString() but still have that error.
Your .ToString() is converting the row value to a string, so you don't also need to cast it on the left with (string)
Ie. if(row["ProductID"].ToString() == txtBarcode.Text)
Personally, I'd stare clear of using == operator with anything but ints, chars and whether this instance is that instance.
A better way of comparing strings is to use string.Equals(string) string.contains(string) or string.indexOf(string)
String.Contains(String) and String.IndexOf(String) are clearly wrong advices, as they return positive results in case of "Foo Bar".IndexOf("Foo");. Better use String.Equals as @Scott suggested.
Note : if you are comparing with TextBox value then it is better to trim the values before comparing to remove the whitespaces using Trim() method.
Solution 1: if you want to find the excat match then you need to use Equals() method.
if(row["ProductID"].ToString().Equals(txtBarcode.Text.Trim())
{
/* do something*/
}
Solution 2: if you want to find the part of the string then you can use String.Contains() method as below:
if(row["ProductID"].ToString().Contains(txtBarcode.Text.Trim())
{
/* do something*/
}
You need to do one of the above. Either do a cast (string)row["ProductId"] or Convert.ToString(row["ProductId"]) for converting the value to string. But casting using (string)row["ProductId"] is likely to throw InvalidCastException. So may be ToString() would be better.
(string)if you are usingToString