C# String Contains() Method

Last Updated : 06 Mar, 2025

In C#, the String.Contains() method is used to check whether a substring exists within a given string. It returns a Boolean value (true or false) indicating whether the substring is found. By default, the method performs a case-sensitive comparison.

Example 1: Here, we are using the String.Contains() method to check if the string contains the specified substring (Case-Sensitive Comparison).

// C# program to demonstrate the 
// String.Contains() Method 
using System; 

class Geeks 
{ 
	public static void Main() 
	{
		// declaring the string
		String str = "GeeksforGeeks"; 
		String s1 = "for"; 
		String s2 = "For"; 
        bool ans;

		// using String.Contains() Method 
		// Here case-sensitive comparison	
		ans = str.Contains(s1);
		Console.WriteLine($"is '{s1}' is present in the '{str}': {ans}");	

		// Here case-insensitive comparison
		// return false because 'For' is not present in the 'GeeksforGeeks' 
		ans = str.Contains(s2);
		Console.WriteLine($"is '{s2}' is present in the '{str}': {ans}"); 
	} 
}

Output

is 'for' is present in the 'GeeksforGeeks': True
is 'For' is present in the 'GeeksforGeeks': False

Syntax of String.Contains() Method

public bool Contains(string str)

Parameter: It takes a single parameter str (string) which is to be checked. Type of this parameter is System.String.
Return Type: Returns a boolean value. If a substring exists in a string or the value is the empty string (“”), then it returns True, otherwise returns False.
Exception: This method can give ArgumentNullException if str is null.

Note: This method performs the case-sensitive checking. The search will always begin from the first character position of the string and continue until the last character position.

Example 2: Use the Contains() method to check the starting index of a substring. If the substring is found, you can also determine its starting index using String.IndexOf().

// C# program to demonstrate the 
// String.Contains() Method 
// along with the starting position 
using System; 

class Geeks
{ 
	public static void Main() 
	{ 
		string str = "Welcome to gfg"; 
		string sub = "gfg"; 

		// Check if the substring is 
		// present in the main string 
		bool b = str.Contains(sub); 

		Console.WriteLine("'{0}' is in the string '{1}': {2}", 
						sub, str, b); 
		if (b) { 
			int index = str.IndexOf(sub); 
			if (index >= 0) 
				Console.WriteLine("{0} begins at character position {1}", 
				sub, index + 1); 
		} 
	} 
}

Output

'gfg' is in the string 'Welcome to gfg': True
gfg begins at character position 12

Example 3: Check whether the substring is present in a string using ordinal comparison and case-insensitive ordinal comparison.

// C# program to demonstrate the 
// String.Contains() Method 
using System;

class Geeks
{
	public static void Main()
	{
		// declaring the string
		String str = "GeeksforGeeks";
		String sub = "For";
		bool ans;

		// Here case-insensitive comparison
		// return false because 'For' is not present in the 'GeeksforGeeks' 
		ans = str.Contains(sub);
		Console.WriteLine($"is '{sub}' is present in the '{str}': {ans}");

		// Ordinal Ignore Case comparison
		ans = str.Contains(sub, StringComparison.OrdinalIgnoreCase);
		Console.WriteLine($"is '{sub}' is present in the '{str}': {ans}");
	}
}

Output

is 'For' is present in the 'GeeksforGeeks': False
is 'For' is present in the 'GeeksforGeeks': True

Stack.Contains() Method in C#

Mithun Kumar

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C# String Contains() Method

Syntax of String.Contains() Method

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