input string was not in a correct format error in C#

Question

I am trying to add the following details into the Database table. The question. the answer and the topicID[int]

C# Code:

private void AddingQuestions()
{
using (MySqlConnection connection = new MySqlConnection("datasource=localhost;port=3306;database=project;username=root;password=***;"))
{
MySqlCommand cmd = new MySqlCommand("INSERT INTO questions (question, answer, topicID) VALUES (@Questions, @Answers, @TopicID);");
cmd.CommandType = CommandType.Text;
cmd.Connection = connection;
cmd.Parameters.AddWithValue("@Questions", TxtBoxQuestion.Text);
cmd.Parameters.AddWithValue("@Answers", TxtboxAnswer.Text);
cmd.Parameters.AddWithValue("@TopicID", Convert.ToInt32(TxtBoxTopicID.Text));
connection.Open();
cmd.Connection = connection;
cmd.ExecuteNonQuery();
MessageBox.Show("Saved");
connection.Close();
}
}

An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll

Additional information: Input string was not in a correct format.

at the Line:

cmd.Parameters.AddWithValue("@TopicID", Convert.ToInt32(TxtBoxTopicID.Text));

Furthermore: I know its good practise to use parametrised sql to avoid sql injections. Am I using parametrised sql?

Make sure that the text in TxtBoxTopicID is a valid integer — Flat Eric
– Flat Eric, Commented Mar 4, 2017 at 16:07
I get this exception before the form is shown. i.e when I click on the button which directs me to this page. The exception is thrown without me even adding any integer value at the textbox. — SnapShot
– SnapShot, Commented Mar 4, 2017 at 16:09
If you have not entered anything yet, the value of the TextBox is null or an empty string, which cannot be converted to int. You should either not call the method when opening the form or fill the textbox with a valid default value — Flat Eric
– Flat Eric, Commented Mar 4, 2017 at 16:12

Flat Eric · Accepted Answer · 2017-03-04 16:21:04Z

1

As discussed in the comments, the problem is that you try to convert the Value of a TextBox that actually does not have a value (it is null or empty string) during opening of the Form

Possible solutions:

Do not call the method during startup of the form
Fill the TextBox with a valid default value

To answer the second part of the question: Yes, you are already using a parameterized query.

answered Mar 4, 2017 at 16:21

Flat Eric

8,1319 gold badges39 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

SnapShot Over a year ago

Yes, the mistake I made was that I called the function in the "load form" function instead of the button. Thanks, very much.

Collectives™ on Stack Overflow

input string was not in a correct format error in C#

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related