how to compare two string in C#

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I have used the following method to compare two string but it will show this string are different

C#

for (int I = 0; I < MacID.Count; I++)
    {
        string t = MacID[I].ToString();
        if (t.ToString()==mac.ToString())
        {
            checkMAC = mac;
        }
        else
        {
            checkMAC = "";
        }
    }

both string contains same value

"001CCO334554"

but result return by this comaparison is false

Posted 8-Apr-12 19:44pm

vrushali katkade

Updated 8-Apr-12 19:48pm

Prasad_Kulkarni

v3

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Philippe Mori 9-Jul-15 12:16pm

If both strings are the same thant the result would be true. If it returns false, then it must be different. Maybe a mix of uppercase and lowercase... In fact, it is easy to see that in your string you mix digit 0 and letter O thus it is not surprising that it does not works.

7 solutions

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Andreas Gieriet · Answer 1 · 2012-04-09T07:20:00

From your post I must make some assumptions - see code below.

As VJ Reddy already suggests in Solution #4, use Contains(...). I would suggest to also check case insensitive:

C#

  1  List<string> macIds = new List<string>
  2  {
  3      "001CCO334550",
  4      "001CCO334551",
  5      "001CCO334552",
  6      "001CCO334553",
  7      "001CCO334554",
  8      "001CCO334555",
  9      "001CCO334556",
 10  };
 11  
 12  string mac = "001ccO334554";
 13  bool found = macIds.Contains(mac, StringComparer.InvariantCultureIgnoreCase);
 14  Console.WriteLine("{0} {1}found", mac, found ? "" : "not ");

Output:

001ccO334554 found

Cheers
Andi

VJ Reddy · Answer 2 · 2012-04-08T20:13:00

As mentioned in the question that both strings contain same value, it appears that MacID, mac and checkMAC are all of string type.
The solution 2 by nawazish12khan works well, as Equals method of string class compares the contents unlike the reference for other reference types, unless it is overridden to compare in another way.
However, I think the following code may also serve the purpose.

C#

string checkMAC = MacID.Contains(mac) ? mac : string.Empty;

lukeer · Answer 3 · 2015-07-09T01:58:00

Since you're talking of MAC addresses, you could get away without all the string comparing. MACs are six bytes. One of them fits nicely in a ulong. Ok, you're wasting two bytes. But that's still a lot better than the string representation.

Get your ulongs via the UInt64.TryParse() method. Comparing those is trivial.

For user convenience, display as hexadecimal again. macValue.ToString("X6") should do the job.

Bojjaiah · Answer 4 · 2012-04-08T19:52:00

Solution 1

see reference

Comparing two Strings[^]

Compare Strings[^]

Posted 8-Apr-12 19:52pm

Bojjaiah

nawazish12khan · Answer 5 · 2012-04-08T19:57:00

Solution 2

C#

for (int I = 0; I < MacID.Count; I++)
{
    string t = MacID[I].ToString();
    if (t.Equals(mac.ToString()))    //Use t.Equals
    {
        checkMAC = mac;
    }
    else
    {
        checkMAC = "";
    }
}

Enjoy...

Posted 8-Apr-12 19:57pm

nawazish12khan

Updated 8-Apr-12 20:11pm

v2

Philippe Mori · Answer 6 · 2015-07-09T06:21:00

In addition to other solutions, we can clearly see that you mix letter O with digit 0. Maybe only one string has this inconsitencies and it might be the reason why they are different.

When writting code, you should use a font that allows you to see the difference between both. Usually, the letter is wider than the digit.

Anup kumar(MCA) · Answer 7 · 2012-04-08T20:31:00

Solution 5

use string.Compare() method

C#

string str1= "test";
string str2= "test";
int i = string.Compare(str1, str2);

it returns int value. 0 in case true else it returns -1.

Posted 8-Apr-12 20:31pm

Anup kumar(MCA)

Updated 8-Apr-12 20:35pm

v2

how to compare two string in C#

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