如何在C＃中比较2个字符串

Question

I have some string like this: str1 = STA001, str2 = STA002, str3 = STA003 and have code to compare strings:

private bool IsSubstring(string strChild, string strParent)
    {
            if (!strParent.Contains(strChild))
            {
                return false;
            }
            else return true;
    }

If I have strChild = STA001STA002 and strParent = STA001STA002STA003 then return true but when I enter strChild = STA001STA003 and check with strParent = STA001STA002STA003 then return false although STA001STA003 have contains in strParent. How can i resolve it?

Answer 1

What you're describing is not a substring . It is basically asking of two collections the question "is this one a subset of the other one?" This question is far easier to ask when the collection is a set such as HashSet<T> than when the collection is a big concatenated string.

This would be a much better way to write your code:

var setOne = new HashSet<string> { "STA001", "STA003" };

var setTwo = new HashSet<string> { "STA001", "STA002", "STA003" };

Console.WriteLine(setOne.IsSubsetOf(setTwo)); // True
Console.WriteLine(setTwo.IsSubsetOf(setOne)); // False

Or, if the STA00 part was just filler to make it make sense in the context of strings, then use int s directly:

var setOne = new HashSet<int> { 1, 3 };

var setTwo = new HashSet<int> { 1, 2, 3 };

Console.WriteLine(setOne.IsSubsetOf(setTwo)); // True
Console.WriteLine(setTwo.IsSubsetOf(setOne)); // False

Answer 2

The Contains method only looks for an exact match, it doesn't look for parts of the string.

Divide the child string into its parts, and look for each part in the parent string:

private bool IsSubstring(string child, string parent) {
  for (int i = 0; i < child.Length; i+= 6) {
    if (!parent.Contains(child.Substring(i, 6))) {
      return false;
    }
  }
  return true;
}

You should however consider it cross-part matches are possible, and if that is an issue. Eg looking for "1STA00" in "STA001STA002" . If that would be a problem, then you should divide the parent string similarly, and only make direct comparisons between the parts, not using the Contains method.

Note: Using hungarian notation for the data type of variables is not encouraged in C#.

Answer 3

This may be a bit on the overkill side, but it might be incredibly beneficial.

private static bool ContainedWord(string input, string phrase)
{
     var pattern = String.Format(@"\b({0})", phrase);
     var result = Regex.Match(input, pattern);

     if(string.Compare(result, phrase) == 0)
          return true;

     return false;
}

If the expression finds a match, then compare the result to your phrase. If they're zero, it matched. I may be misunderstanding your intent.