How can I do a case insensitive string comparison?

Question

How can I make the line below case insensitive?

drUser["Enrolled"] = 
      (enrolledUsers.FindIndex(x => x.Username == (string)drUser["Username"]) != -1);

I was given some advice earlier today that suggested I use:

x.Username.Equals((string)drUser["Username"], StringComparison.OrdinalIgnoreCase)));

the trouble is I can't get this to work, I've tried the line below, this compiles but returns the wrong results, it returns enrolled users as unenrolled and unenrolled users as enrolled.

drUser["Enrolled"] = 
      (enrolledUsers.FindIndex(x => x.Username.Equals((string)drUser["Username"], 
                                 StringComparison.OrdinalIgnoreCase)));

Can anyone point out the problem?

Answer 1

I think you will find more information in this link:

http://codeidol.com/community/dotnet/controlling-case-sensitivity-when-comparing-two-st/8873/

Use the Compare static method on the String class to compare the two strings. Whether the comparison is case-insensitive is determined by the third parameter of one of its overloads. For example:

string lowerCase = "abc";
string upperCase = "AbC";
int caseInsensitiveResult = string.Compare(lowerCase, upperCase,
  StringComparison.CurrentCultureIgnoreCase);
int caseSensitiveResult = string.Compare(lowerCase,
  StringComparison.CurrentCulture);

The caseSensitiveResult value is -1 (indicating that lowerCase is "less than" upperCase) and the caseInsensitiveResult is zero (indicating that lowerCase "equals" upperCase).

Answer 2

Please use this for comparison:

string.Equals(a, b, StringComparison.CurrentCultureIgnoreCase);

Answer 3

How about using StringComparison.CurrentCultureIgnoreCase instead?

Answer 4

Others answer are totally valid here, but somehow it takes some time to type StringComparison.OrdinalIgnoreCase and also using String.Compare.

I've coded simple String extension method, where you could specify if comparison is case sensitive or case senseless with boolean, attaching whole code snippet here:

using System;

/// <summary>
/// String helpers.
/// </summary>
public static class StringExtensions
{
    /// <summary>
    /// Compares two strings, set ignoreCase to true to ignore case comparison ('A' == 'a')
    /// </summary>
    public static bool CompareTo(this string strA, string strB, bool ignoreCase)
    {
        return String.Compare(strA, strB, ignoreCase) == 0;
    }
}

After that whole comparison shortens by 10 characters approximately - compare:

Before using String extension:

String.Compare(testFilename, testToStart,true) != 0

After using String extension:

testFilename.CompareTo(testToStart, true)

Answer 5

you can always use functions: .ToLower(); .ToUpper();

convert your strings and then compare them...

Good Luck

Answer 6

You should use static String.Compare function like following

x => String.Compare (x.Username, (string)drUser["Username"],
                     StringComparison.OrdinalIgnoreCase) == 0