How to check string is number or not in C#

How to check string is number or not in C#

• Julio Casal T.

  If you are using the new .NET Framework 2.0 (C# 2005), then below code will work for you:

• Jennifer Bhamoo

  Exceptions should be just that - exceptions. Would you regard it as exceptional that an expression is passed to this routine that is not numeric

  An IsNumeric in C# which does not rely on unexceptional exception logic is:http://www.tangiblesoftwaresolutions.com/Articles/CSharp%20Equivalent%20to%20IsNumeric.htm

  
  
  

• BillyTheGate

  In the TextBox_TextChange check the charater by using the following code

  for (int i=0; i<this.textbox1.text.length; i++)

  {

  if (char.IsDigit(this.textbox1.text)==false)

  // give any error

  }

  
  
  

• Robin Charisse

  Here's a nice implementation from the guys at sadeveloper.net:
  
  public static System.Boolean IsNumeric (System.Object Expression)
  {
  if(Expression == null || Expression is DateTime)
  return false;
  
  if(Expression is Int16 || Expression is Int32 || Expression is Int64 || Expression is Decimal || Expression is Single || Expression is Double || Expression is Boolean)
  return true;
  
  try
  {
  if(Expression is string)
  Double.Parse(Expression as string);
  else
  Double.Parse(Expression.ToString());
  return true;
  } catch {} // just dismiss errors but return false
  return false;
  }
  }
  
  
  

• BigT4446

  Within your method, an exception occurs for most cases where the expression is not numeric. You catch the exception within the method. The fact that you don't throw the exception further is not the issue.

  Run a test with both methods and you'll see that with relatively few iterations, the one that relies on exceptions is very slow when the expression is not numeric. For example, at fewer than 100 iterations you can see an obvious difference. If you have this "unexceptional exception" approach throughout your code, you will have performance issues.

  David Anton
  www.tangiblesoftwaresolutions.com
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• Manoj K Srivastava

  Yip, it's the best way
  
  
  

• Corby

  If you're using .NET 1.1 then I like the following code...
  
  bool textIsNumeric = true;
  try
  {
  int.Parse(TextBox1.Text);
  }
  catch
  {
  textIsNumeric = false;
  }
  
  I know you said you didn't want to use try/catch but this is simple and effective.
  
  
  
  

• Clive Townsend

  How am I "forcing" an exception I am in fact *preventing* an exception from being thrown.
  Yes, you're right! The TryParse method on double is available in framework 1.1.
  
  
  

• meatago

  Ah, I see what you mean. Sure, the creation of the exception (by Double.Parse) would be expensive.
  Without using TryParse, however, this is the only way I can see it happening.
  
  
  

• BanyiX

  Hi!
  Thanks for all of you.
  I tried it and it solve my problem. In .Net 1.1, Double.TryParse use four paremeters so follows:
  Double.TryParse(Str, System.Globalization.NumberStyles.Any, System.Globalization.CultureInfo.CurrentCulture, out Num)
  
  Thank again!
  
  CLC
  
  

• root16749

  This will not work if the user hits a character that is not a digit but it could be in a number like the dot '.' character or the negative/minus '-' character.

• fishandchips

  That's why double.TryParse is a good option.
  
  

• rob_a89

  But within the method you are forcing an exception to occur when the expression is not numeric. Forcing exceptions as part of normal logic flow when there is a more efficient alternative is something I wouldn't recommend.

  Double.TryParse is available in 1.1 (and 1.0 also).

  David Anton
  www.tangiblesoftwaresolutions.com
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• Tim Daley

  "Would you regard it as exceptional that an expression is passed to this routine that is not numeric "

  No, which is exactly why I don't throw the exception. If an exception is caught, the string is obviously NOT numeric, and the method should return false. This is a perfectly acceptable case for not throwing an exception.

  Note that the example you posted will only work on .NET framework 2, where the TryParse methods are available.

  
  
  
• How to check string is number or not in C#