如何在C＃中比较两个字符串 [英] how to compare two string in C#

问题描述

我使用以下方法比较两个字符串，但它会显示此字符串不同

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

两个字符串包含相同的值

001CCO334554

但是这个comaparison的结果返回是假的

解决方案

从你的帖子我必须做一些假设 - 见下面的代码。



正如VJ Reddy已经在解决方案＃4中建议的那样，使用包含（...）。我建议也检查不区分大小写：

  1 列表< string> macIds =  new 列表< 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。包含（mac，StringComparer.InvariantCultureIgnoreCase）; 
  14  Console.WriteLine（  {0 } {1}发现，mac，found？ ：  not）; 
 

输出：

 001ccO334554 found 

干杯

Andi

如问题所述，两个字符串都包含相同内容值，似乎 MacID，mac和checkMAC 都是 string 类型。

nawazish12khan 的解决方案2运行良好，因为等于 字符串类的方法比较内容与其他参考类型的参考不同，除非它被覆盖以便以另一种方式进行比较。

但是，我认为以下代码也可用于此目的。

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

既然你在谈论MAC地址，你可能会得到没有所有的字符串比较。 MAC是六个字节。其中一个非常适合 ulong 。好的，你浪费了两个字节。但是这仍然比字符串表示好很多。



通过 UInt64.TryParse（）方法。比较这些是微不足道的。



为方便用户，再次显示为十六进制。 macValue.ToString（X6）应该完成这项工作

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

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

解决方案

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:

  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

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.

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

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.

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