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C# checking input value

I have a text box as an input field...
I basically want to check if the input is a 7 digit number or a 7 digit number such as this 333.4444. Separated by a dot.

Is there a way to do this in the code behind?

RealMrTea

If you are talking about an ASP.NET page...you can use a regular expression validator.

Otherwise you could use a regular expression.

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RealMrTea

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jatinderalagh

string test = "333.4444";
                  int counter = 0;
                  for(int i=0; i<test.Length; i++)
                  {
                        if(char.IsNumber(test,i)) counter++;
                  }
                  if(counter == 7)
                  {
                        MessageBox.Show("Test Successfull.");
                  }
                  else
                  {
                        MessageBox.Show("Test failed.");
                  }

puranik_p

Just an addition to jatinderalagh's solution.
also check for IsNumber for the whole number.
Otherwise "333A4444" will also show "Test Successfull"

Bob Learned

Would 3333.444 be okay? How about 33333.44?

@jatinderalagh:
Does IsNumber return true or false for decimal '.'.

Is this an international application? Maybe the decimal is a comma ','.

Bob

jatinderalagh

@Bob

[C#] public static bool IsNumber(char);
Indicates whether the specified Unicode character is categorized as a number.
Supported by the .NET Compact Framework.

[C#] public static bool IsNumber(string, int);
Indicates whether the character at the specified position in a specified string is categorized as a number.
Supported by the .NET Compact Framework.

As it supports the unicode characters. So it does not matter whether it's a international appplication or not.

Jatinder

Bob Learned

What I am trying to ask is:

What is the result of IsNumber(".") or IsNumber(",")? Because you are not looking at the string as a whole, but each individual character.

Bob

jatinderalagh

false

Bob Learned

This should return false for 333A4444, but since it only counts for 7 numeric values, then this would be seen as valid (from puranik_p comment).

@puranik_p:
How would you check IsNumber with the entire string? It is char.IsNumber, not string.IsNumber.

Code modificatiion from jatinderalagh's code (not for points):

string test = "333A4444";

bool valid = true;
int counter = 0;

char dec = System.Globalization.NumberFormatInfo.CurrentInfo.NumberDecimalSeparator.ToCharArray()[0];

foreach (char ch in test.ToCharArray())
{

bool numeric = char.IsNumber(ch);

if (ch != dec)

if (!numeric)
{
valid = false;
break;
}
else if (numeric)
counter +=1;

}

if (valid && counter == 7)
MessageBox.Show("Test successful.");
else
MessageBox.Show("Test failed.");

Bob

RealMrTea

Actually...I think this expression would work a little better.
"[0-9]{3}[.][0-9]{4}"

puranik_p

@Bob,
>It is char.IsNumber, not string.IsNumber
I was thinking about IsNumeric (VB) when I posted this.

Thanks for correcting.
Pura