How to check for variable character in string and match it with another string of same length?

Question

I have a rather complex issue that I'am unable to figure out.

I'm getting a set of string every 10 seconds from another process in which the first set has first 5 characters constant, next 3 are variable and can change. And then another set of string in which first 3 are variable and next 3 are constant.

I want to compare these values to a fixed string to check if the first 5 char matches in 1st set of string (ABCDE*** == ABCDEFGH) and ignore the last 3 variable characters while making sure the length is the same. Eg : if (ABCDE*** == ABCDEDEF) then condition is true, but if (ABCDE*** == ABCDDEFG) then the condition is false because the first 5 char is not same, also if (ABCDE*** == ABCDEFV) the condition should be false as one char is missing.

I'm using the * in fixed string to try to make the length same while comparing.

Answer 1

Does this solve your requirements?

private static bool MatchesPattern(string input)
{
    const string fixedString = "ABCDExyz";
    return fixedString.Length == input.Length && fixedString.Substring(0, 5).Equals(input.Substring(0, 5));
}

In last versions of C# you can also use ranges:

private static bool MatchesPattern(string input)
{
    const string fixedString = "ABCDExyz";
    return fixedString.Length == input.Length && fixedString[..5].Equals(input[..5]);
}

See this fiddle .

BTW: You could probably achieve the same using regex.

Answer 2

If the string you match against is known at compile time, your best bet is probably using regular expressions. In the first case, match against ^ABCDE...$ . In the second case, match against ^...DEF$ .

Another way, probably better if the match string is unknown, uses Length, StartsWith and EndsWith:

String prefix = "ABCDE";
if (str.Length == 8 && str.StartsWith(prefix)) {
    // do something
}

Then similarly for the second case, but using EndsWith instead of StartsWith.

Answer 3

It's always a good idea to make an abstraction. Here I've made a simple function that takes the pattern and the value and makes a check:

bool PatternMatches(string pattern, string value)
{
    // The null string doesn't match any pattern
    if (value == null)
    {
        return false;
    }
    // If the value has a different length than the pattern, it doesn't match.
    if (pattern.Length != value.Length)
    {
        return false;
    }
    // If both strings are zero-length, it's considered a match
    bool result = true;
    // Check every character against the pattern
    for (int i = 0; i< pattern.Length; i++)
    { 
        // Logical and the result, * matches everything
        result&= (pattern[i]== '*') ? true: value[i] == pattern[i];
    }
    return result;
}

You can then call it like this:

bool b1 = PatternMatches("ABCDE***", "ABCDEFGH");
bool b2 = PatternMatches("ABC***", "ABCDEF");

You could use regular expressions, but this is fairly readable, RegExes aren't always.

Here is a link to a dotnetfiddle: https://dotnetfiddle.net/4x1U1E

Answer 4

check this

public bool Comparing(string str1, string str2)
  => str2.StartWith(str1.replace("*","")) && str1.length == str2.Length;