Contains

This C# method searches strings. It checks if one substring is contained in another. It also provides a case-sensitive ordinal method for checking string contents.

Contains returns true or false, not an index. It is the same as calling IndexOf and testing for -1 on your own. But Contains can be clearer to read.

Example

Contains is an instance method—you can call it on a specific string in your program. It has a bool result, which is true if the parameter is found, and false if it is not found.

using System;

string value = "abcdef";
if (value.Contains("abc"))
{
    Console.WriteLine("CONTAINS abc");
}
if (!value.Contains("xyz"))
{
    Console.WriteLine("DOES NOT CONTAIN xyz");
}
if (value.Contains("ABC", StringComparison.OrdinalIgnoreCase))
{
    Console.WriteLine("CONTAINS ABC ignore case");
}
CONTAINS abc
DOES NOT CONTAIN xyz
CONTAINS ABC ignore case

Contains extension

This program tests the Contains extension method, which is a separate Contains from the string method. The extension method can be used on many types.

using System;
using System.Collections.Generic;
using System.Linq;

var list = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
// Use extension method.
bool a = list.Contains<int>(7);
// Use instance method.
bool b = list.Contains(7);

Console.WriteLine(a);
Console.WriteLine(b);
True
True

List Contains

There is also a Contains method on the C# List type. This method can be useful for searching for a value within a List.

Summary

The simplest method to perform a task is often the best one. Contains is a simplified version of IndexOf. It allows you to easily check whether a string is contained in another.