.NET string.IsNullOrWhiteSpace implementation

Question

Folks, I was looking at the implementation of string.IsNullOrWhiteSpace in:

http://typedescriptor.net/browse/types/9331-System.String

Here is the implementation:

public static bool IsNullOrWhiteSpace(string value)
{
    if (value == null)
    {
        return true;
    }
    for (int i = 0; i < value.Length; i++)
    {
        if (char.IsWhiteSpace(value[i]))
        {
        }
        else
        {
            goto Block_2;
        }
    }
    goto Block_3;
    Block_2:
    return false;
    Block_3:
    return true;
}

Question: Isn't this over complicated? Can't the following implementation do the same job and be easier on the eye:

bool IsNullOrWhiteSpace(string value)
{
    if(value == null)
    {
        return true;
    }   
    for(int i = 0; i < value.Length;i++)
    {
        if(!char.IsWhiteSpace(value[i]))
        {
            return false;
        }
    }
    return true;
}

Is this implementation incorrect? Does it have a performance penalty?

That's essentially what it is doing - you are not looking at the real source code, just what was gathered from reflection — BrokenGlass
– BrokenGlass, Commented Apr 20, 2012 at 17:57

SLaks · Accepted Answer · 2012-04-20 17:58:09Z

19

The original code (from the reference source) is

public static bool IsNullOrWhiteSpace(String value) {
    if (value == null) return true; 

    for(int i = 0; i < value.Length; i++) { 
        if(!Char.IsWhiteSpace(value[i])) return false; 
    }

    return true;
}

You're seeing the output of a poor decompiler.

answered Apr 20, 2012 at 17:58

SLaks

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6 Comments

The Muffin Man Over a year ago

Note that this could be considerably shortened with the following code: return value == null || value.All(Char.IsWhiteSpace);

Caleb Bell Over a year ago

@SLaks - Could you add a link to or documentation on "the reference source"?

SLaks Over a year ago

@CalebBell: referencesource.microsoft.com/#mscorlib/system/…

SLaks Over a year ago

For more information, see blog.slaks.net/2014-02-24/inside-the-new-net-reference-source

Issung Over a year ago

Could be shorter now too with return value?.All(Char.IsWhiteSpace) ?? true;

|

Chris Shain · Accepted Answer · 2012-04-20 17:57:10Z

8

You are looking at C# that was recreated from the disassembled IL. I am sure that the actual implementation is closer to your example and does not use labels.

answered Apr 20, 2012 at 17:57

Chris Shain

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Comments

Pranav Shah · Accepted Answer · 2012-04-20 18:11:00Z

3

Shown below is an extension method I needed for older versions. I am not sure where I obtained the code from:

public static class StringExtensions
    {
        // This is only need for versions before 4.0
        public static bool IsNullOrWhiteSpace(this string value)
        {
            if (value == null) return true;
            return string.IsNullOrEmpty(value.Trim());
        }
    }

answered Apr 20, 2012 at 18:11

Pranav Shah

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Comments

500 - Internal Server Error · Accepted Answer · 2014-03-07 20:16:39Z

3

It must be typedescriptor's disassembler doing that.

When I look at the same function with JetBrain's dotPeek it looks like this:

 public static bool IsNullOrWhiteSpace(string value)
    {
      if (value == null)
        return true;
      for (int index = 0; index < value.Length; ++index)
      {
        if (!char.IsWhiteSpace(value[index]))
          return false;
      }
      return true;
    }

edited Mar 7, 2014 at 20:16

answered Apr 20, 2012 at 18:02

500 - Internal Server Error

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