CODEWITHSUNDEEP
c#substring
Ali Kleit
Ali Kleit

Reputation: 3649

Substring the first occurrence of each part of a string in another string in c#

I have these two strings:

  1. "Project.Repositories.Methods"
  2. "Project.Repositories.DataSets.Project.Repositories.Entity"

I want to trim the first occurrence (from the first index in 2) of parts of string 1 in string 2, so the desired result would be:

"DataSets.Project.Repositories.Entity"

What is the best way of doing this?

Upvotes: 1

Views: 209

Answers (2)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186698

It's not clear what do you mean by "best way"; if you want to Split each string by . and get rid of common chunks, i.e.

  Project        Project       - these chunks should be 
  Repositories   Repositories  - removed (they are same in both strings)
  Methods        DataSets
                 Project
                 Repositories
                 Entity

you can try using Linq e.g.

  using System.Linq;

  ...

  string prefix = "Project.Repositories.Methods";
  string source = "Project.Repositories.DataSets.Project.Repositories.Entity";

  string[] prefixes = prefix.Split('.');

  string result = string.Join(".", source
    .Split('.')                                            // split into 
    .Select((value, index) => new { value, index})         // chunks  
    .SkipWhile(item => item.index < prefixes.Length &&     // skip
                       prefixes[item.index] == item.value) // common chunks
    .Select(item => item.value));

  Console.Write(result);

Outcome:

  DataSets.Project.Repositories.Entity

Edit: No Linq solution, inspired by urbanSoft's answer:

  string prefix = "Project.Repositories.Methods";
  string source = "Project.Repositories.DataSets.Project.Repositories.Entity";

  // We have 2 cases when all starting characters are equal:
  string result = prefix.Length >= source.Length 
    ? ""
    : source.Substring(source.IndexOf('.', prefix.Length) + 1);

  for (int i = 0, dotPosition = -1; i < Math.Min(prefix.Length, source.Length); ++i) {
    if (prefix[i] != source[i]) {
      result = source.Substring(dotPosition + 1);

      break;
    }
    else if (prefix[i] == '.')
      dotPosition = i;
  }

  Console.Write(result);

Upvotes: 6

urbanSoft
urbanSoft

Reputation: 760

No just the first parts

If only the first parts do matter why not simply iterate until the first character mismatch?

Updated my answer to take @Dmitry Bychenko comments into account.

string a = "Project.Repositories.Data";
string b = "Project.Repositories.DataSets.Project.Repositories.Entity";
int dotIdx = 0;
for (int i = 0; i < a.Length; i++)
    if (a[i] != b[i])
        break;
    else
        dotIdx = a[i] == '.' ? (i+1) : dotIdx;
Console.WriteLine(b.Substring(dotIdx));

Upvotes: 0

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