validate a textbox 123456M

[jasonmrc]

hi

i am trying to validate a id card textbox with the format 123456m

i want to check and if it is not in that format show a messagebox invalid input.

how can i read char [7] and compare it to a deafult char m

your input is appreciated.

[nmaillet]

txtBox.Text[6] == 'm';

That should work for you. If you are checking for numbers as well, you can iterate through the characters in the string (returned by the TextBox.Text property) and use char.IsNumber().

[jasonmrc]

hi thanks for your reply

i was reasoning on these lines

char G = "g";
char M = "m";



   if  textbox.text[6] == m || g {

        messagebox.show( " iD is ok ");

}

else 
      messagebox.show( " Please input a valid iD ");

[james6754]

HMMM..well what you are doing there is trying to put a string value in to a char type...

use single quotation marks...like this...

char G = 'g';
char M = 'm';

if ((textbox.text[6] == m) || (textbox.text[6] == g))
 {

messagebox.show( " iD is ok ");

}

else 
messagebox.show( " Please input a valid iD ");

remember if an id does not have the m or g in the 7th (or 6th) position in your char array, your going to run in to problems. What you could do is use string values....check what position the m or g is at then decide whether to let it go or throw exception etc...

hope this helps

[nmaillet]

You should definitely add a check to ensure there is 7 characters in the string, otherwise you will get an out of bounds exception:

...
if (textBox.Text.Length >= 7 && (textBox.Text[6] == M || textBox.Text[6] == G))
...

[Momerath]

Using a regular expression is easier:

if (Regex.Match(textBox.Text, @"^\d{6}[mg]$").Length > 0) {
    // it's a good ID number
}

This expression requires that there be 6 digits followed by either an 'm' or a 'g'. That is also the only thing allowd ("123456mt" doesn't work, where it would work with the other methods given here).

[jasonmrc]

hi again

i am getting compilation errors
this is the complete method

it is saying that the name 'm' does not exist in the current context

{
             string _numberIn = numberIn;
            int count = 0;
             Boolean isValid = false;

             do
             {
                /*if (!char.IsNumber(_numberIn[count]))
                 {
                     MessageBox.Show("Please input a valid number");
                 }
                 count++;

                 if (count == 7) {
                  */
                   if (txtboxIdcard.Text.Length >= 7 && (txtboxIdcard.Text[6] == M || txtboxIdcard.Text[6] == G))
                                                               
                     {
                      MessageBox.Show("The id card is valid");
                 }

             }
             while ((count < _numberIn.Length) && (isValid == false));

         }

[Momerath]

You need to put ' marks around character constants (the M and the G should look like 'M' and 'G').

[jasonmrc]

thanks for you comment , it is working now

now i have to sort when user inputs just text or just numbers/

[rikthefrog]

Hi i should use regulair expressions as stated earlier. This will make you life in these kinds of problems much easier. I undstand that the learning curve is a little bit steeper, but the investment is worthwhile. I can tell you that from experience.
Bing around, the G word is a little bit difficult on this website ;) for regulair expressions and there are tons of very helpfull sites.