C# String Contains() Method (original) (raw)

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# `

// 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# `

// 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# `

// 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