TextBox entry Validation based on SQL data object

Question

Im validating user entered text, entered into a textbox, to filter out non-numbers,and then compare >= / < to an object pulled from a database. My issue is happening in 2 places though it may be just 1 issue. I have a conversion of a data table item into a string, then into an int. This int is then passed into a series of if /else statements that should validate the users input. After stepping through the program it hits my conversion statement appears to do the conversion, then proceeds to skip my if /else statements.

   int classRPM;
        int fanRPM;
        string actualdata = string.Empty;
        char[] entereddata = txfanrpm.Text.ToCharArray();
        foreach (char aChar in entereddata.AsEnumerable())
        {
            if (Char.IsDigit(aChar))
            {
                actualdata = actualdata + aChar;

                using (Fanrpm ds = new Fanrpm(cbdesigntype.SelectedValue.ToString(), cbfansize.SelectedValue.ToString(), cbfanclass.SelectedValue.ToString()))
                {
                    DataTable dt = ds.dataset.Tables[0];
                    classRPM = Convert.ToInt32(dt.Rows[0].Field<string>("ClassRPM"));

                   // MessageBox.Show(aChar.ToString());
                    fanRPM = Convert.ToInt32(actualdata);
                    if (fanRPM >= classRPM)
                    {
                        MessageBox.Show("hi");
                    }
                    else if (fanRPM < classRPM)
                    {
                        MessageBox.Show("Hide");
                    }
                }
            }
            else
            {
                MessageBox.Show(aChar + " is not numeric");
                actualdata.Replace(aChar, ' ');
                actualdata.Trim();
            }
        }
        txfanrpm.Text = actualdata;

What do you mean by "proceeds to skip my if /else statements."? — Andrew Barber
– Andrew Barber, Commented Aug 6, 2014 at 19:58
as in the program does not step through it to either show the messagebox of hi or hide. IT does do the first and last if/else as any non number will prompt the * is not numeric else. — Himarm
– Himarm, Commented Aug 6, 2014 at 20:00
Do you have this code wrapped in an exception handler? Are you stepping through the code? Did you see a message when you had your MessageBox.Show(aChar.ToString()); code there? — Andrew Barber
– Andrew Barber, Commented Aug 6, 2014 at 20:06
Use the debugger. Set a breakpoint on the for line (F9) then step through your code with F10. Be sure to have checked DEBUG->Exceptions->Common Language Runtime Exceptions for User Unhandled. When the error hits you should be able to see the reason in exception message property. — Steve
– Steve, Commented Aug 6, 2014 at 20:09
That piece of code (MessageBox.Show(aChar.ToString())) was a mistake that it got uncommented, while it was uncommented it did nothing and was also skiped, there is no error handling yet. — Himarm
– Himarm, Commented Aug 6, 2014 at 20:11

Steve · Accepted Answer · 2014-08-06 20:49:02Z

After the comments above I think you could change your code in this way

// If the reading from the database gives always the same value is not correct to 
// exexute this code inside the foreach. Just do it one time here and go on....

float classRPM = 0.0f;
using (Fanrpm ds = new Fanrpm(cbdesigntype.SelectedValue.ToString(),
                              cbfansize.SelectedValue.ToString(), 
                              cbfanclass.SelectedValue.ToString()))
{
     DataTable dt = ds.dataset.Tables[0];
     classRPM = dt.Rows[0].Field<float>("ClassRPM");
}

float fanRPM;
string actualdata = string.Empty;

// No need to use AsEnumerable.... 
// And also this code could be easily replaced by single line float.TryParse 
// if you don't need to show a message box for every wrong char....
foreach (char aChar in txfanrpm.Text.ToCharArray())
{
    if (Char.IsDigit(aChar))
        actualdata = actualdata + aChar;
    else
        MessageBox.Show(aChar + " is not numeric");
}
// Now you could start your comparisons....
fanRPM = Convert.ToSingle(actualdata);
if (fanRPM >= classRPM)
   MessageBox.Show("hi");
else
   MessageBox.Show("Hide");

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