Problem with conversion from object to int32

Question

Hello I once thought that I solved this problem but I got it again and I don't know what is the problem. When I put only pom = distpostSqlCommand1.ExecuteScalar() TextBox4.Text = pom.ToString(); I get correct value in my textbox but when I try to convert it in Int32 since I need it to compare with a minimum value and use Int32 rast = Convert.ToInt32(pom); I get an error: Exception Details: System.InvalidCastException: Object cannot be cast from DBNull to other types. Source Error: Line 119: TextBox4.Text = pom.ToString(); Line 120: Int32 rast = Convert.ToInt32(pom);

Sam Hobbs · Answer

First note that DBNull is not the same as null. Second you should use try/catch blocks more. Third people should use Int32.TryParse more often instead of Convert.ToInt32. I have not seen people ask for help when they use Int32.TryParse.

Nel · Answer

Thank you very much Sam again. May I ask you one more question please? Is it good to work with embedded SQLDataReaders or not? I have a while loop where I find elements with the help of stored procedure. So I am wondering whether it is better to make it as a string of elements and put a counter inside the while loop close the loop and start another one for finding the min distance or I can insert another dataReader inside the first while loop for the first DataReader and chack which of the elements is with min. distance using the second stored procedure. Thank you very much in advance.

Sam Hobbs · Answer

With a little more experience you will know how to check for problems and exceptions. The important part is to think ahead about possibilities and that is something experience will really help with. Developers often prefer to hope for the best and not prepare for problems but if you get in the habit of checking for errors it will make everything easier.

Nel · Answer

Thank you very much Sam for your suggestions. They are always welcome especially since I am new in all this. I will have all this on mind and correct my code:) Thanks again.

Nel · Answer

Thank you to all of you. I found the problem in the textbox value.

John Penn · Answer

If you get the correct value in your textbox from this: TextBox4.Text = pom.ToString(); Then this should work too: Int32 rast = Convert.ToInt32(pom.ToString());

Nel · Answer

If I put a check whether it is null it behaves as if it was but in the text box if I don't use the conversion when pomalor object is shown in the textbox it is a correct value

Ankit Nandekar · Answer

check pom variable's value i think it is null so before convesion check wither it is null or not.and then apply conversion

Jiteendra Sampathirao · Answer

Hi you must check if it is equal to DBNull first because DBNull does not equal null. check the condition before assigning the value. if ( XXXXX != System.DBNull.Value) { }

Vijay Yadav · Answer

Hi can please tell what is pom here? or else you can directly convert the TextBox4.Text = convert.ToInt32(distpostSqlCommand1.ExecuteScalar()) and i would suggest before doing this just check whether the executescalar is null or not.