Validate that a given string (name) meets certain requirements

Question

String Name = "yyyy MM DD abjwg kelk.exe"

public static bool IsNameRight(string Name)
{
    string[] temp = Name.Split(' ');
    string[] de= Name.Split('.');

    if (de[1] == "pdf" && temp .Length == 5)
    {
        if (temp [0].Length == 4
            && temp [1].Length == 2 
            && temp [3].Length == 2
            && temp [4] == "abjwg" 
            && temp [5] == "kelk.exe")
            return true;
        else
            return false;
    }
    return false;
}

I am using .NET 3.5 and C#

EDIT

You could use Regular expressions but I have never used it or know how to use it, and don't know if it is a good practice.

Answer 1

The method name would be better called IsNameValid and the parameter name should be camel cased.

public static bool IsNameValid(string name)
{
    // firstly always validate parameters, either throw an exception or return false.
    if (name == null) { throw new ArgumentNullException("name"); }

    // use more descriptive variable names, what does 'de' mean?
    string[] temp = name.Split(' ');
    string[] de= name.Split('.');

    // check that the arrays contain the correct number of values or you will get an exception accessing the indexer.
    if (de.Lengh < 2 || temp.Length < 5) { return false; }

    return de[1] == "pdf"
            && temp[0].Length == 4
            && temp[1].Length == 2 
            && temp[2].Length == 2
            && temp[3] == "abjwg" 
            && temp[4] == "kelk.exe";
}

Answer 2

As you wanted to use RegEx I have a recommendation for you:

public static bool IsValidName(string Name)
{
    if(String.IsNullOrEmpty(Name))
        return new ArgumentNullException();

    string pattern = @"^[0-9]{4} [0-9]{2} [0-9]{2} abjwg kelk\\.exe$";
    return Regex.IsMatch(Name, pattern);
}

Answer 3

If you are trying to get the extension of a file, I would use

System.Io.Path.GetExtension

Update

Since de seem to only be used for getting the extension.

string[] de= Name.Split('.');

could be changed to

string de = System.Io.Path.GetExtension(Name);

Answer 4

private static readonly Regex pattern = new Regex(@"[0-9]{4} [0-9]{2} [0-9]{2} [A-Za-z0-9]{5} [A-Za-z0-9]{4}\.exe");

public static bool IsNameRight(string name)
{
    return pattern.IsMatch(name);
}

• [0-9] means a character which is a digit between 0 and 9.
• [A-Za-z0-9] means a character which is between A and Z (uppercase) or a and z (lowercase) or a digit between 0-9.
• {4} exactly four times

Answer 5

I can think of at least few things with the code. Skip some of the redundant else and if clasues.

String name = "yyyy MM DD abjwg kelk.exe"

public static bool IsNameRight(string Name)
{
    string[] temp = Name.Split(' ');
    string[] de = Name.Split('.');

    if (de[1] != "pdf" && temp.Length != 5)
      return false;

  if (temp [0].Length == 4
    && temp [1].Length == 2 
    && temp [3].Length == 2
    && temp [4] == "abjwg" 
    && temp [5] == "kelk.exe")
    return true;
  return false;
}

Answer 6

Here's another way of improving your code:

String name = "yyyy MM DD abjwg kelk.exe"

public static bool isNameRight( string name )
{
    string[] de   = name.Split( "." );
    string[] temp = de[0].Split( " " );

    if ( ! ( de[1] == "pdf" && temp.Length == 5 ) )
        return false;

    return ( temp[0].Length == 4
                && temp[1].Length == 2 
                && temp[2].Length == 2
                && temp[3] == "abjwg" 
                && temp[4] == "kelk" );
}

I know this isn't about finding and fixing bugs, but it seemed important to note that given your name string and your function logic, it will always return false, because you're testing for temp [5] == "kelk.exe" after de[1] == "pdf" so in this case, if de[1] equals "pdf" then temp[5] will never have the .exe part, it would have .pdf. That's also why I removed the extension from temp[4] value.

Additionally, I would use @the_lotus way of dealing with the file extension.

I hope you find this helpful.