Proposal: String.Contains(char) #24068
Description
Rationale and Usage
Finding a character in a string is a fairly common primitive operation. Unfortunately we lead users to the pit of failure because mystring.Contains(char) will bind to the Linq version, which can easily be 20x slower than mystring.IndexOf(char) != -1. By adding these to string, the next recompile will give a performance improvement.
Proposed API
public sealed partial class String : System.Collections.Generic.IEnumerable<char>, System.Collections.IEnumerable, System.IComparable, System.IComparable<string>, System.IConvertible, System.IEquatable<string>, System.ICloneable
{
public bool Contains(char value) { throw null; }
public bool Contains(char value, StringComparison comparisonType) { throw null; }
public bool Contains(string value) { throw null; } // already exists
public bool Contains(string value, StringComparison comparisonType) { throw null; } // already exists
public int IndexOf(char value, StringComparison comparisonType) { throw null; } // to implement above
}the implementations will simply be
public bool Contains(char value)
{
return IndexOf(value) != -1;
}
public bool Contains(char value, StringComparison comparisonType)
{
return IndexOf(value, comparisonType) != -1;
}Microbenchmark
Searching in 10 and 1000 character strings:
Method | Mean | Error | StdDev |
---------- |-----------:|----------:|----------:|
LinqShort | 142.750 ns | 0.4997 ns | 0.4430 ns |
LinqLong | 180.121 ns | 0.4741 ns | 0.3428 ns |
FastShort | 7.575 ns | 0.0196 ns | 0.0174 ns |
FastLong | 8.508 ns | 0.0403 ns | 0.0377 ns |
Variations
The StringComparison overload is in order to search case insensitively if desired. The IndexOf overload is needed to implement it. These could be discarded as the 90% case I would expect to not take a comparison.