In Windows forms C#, I want to check if a textbox I made starts with a numeric value, then if it does I want to insert the minus (-) sign at the beginning to change the number to negative, I found a way but it's too time wasting, here's my code:
if (richTextBox1.Text.StartsWith("1") || richTextBox1.Text.StartsWith("2") #until richTextBox1.Text.StartsWith("9")) { richTextBox1.Text.Insert(0, "-"); } So I was asking, if there's a shorter way to replace that code?
if (Char.IsNumber(richTextBox1.Text[0]))... You should also add some checks around it to make sure there's text.
Using regex:
if (Regex.IsMatch(richTextBox1.Text, @"^\d")) Matches a digit (0-9) at the start of the string.
Or a direct replace:
richTextBox1.Text = Regex.Replace(richTextBox1.Text, @"^\d", "-$&"); Checking if the first character of a text is a number can be done in single line, using Char.IsNumber() function as follows:
if ( Char.IsNumber( stringInput, 0) ) {
// String input begins with a number}
More information: https://learn.microsoft.com/en-us/dotnet/api/system.char.isnumber
Many good answer's already here, another alternative is if you want culture support give this a try...
public static bool IsNumber(char character) { try { int.Parse(character.ToString(), CultureInfo.CurrentCulture); return true; } catch (FormatException) { return false; } } You can call it like:
if ( IsNumber(richTextBox1.Text[0]))