C# .Contains()

The .Contains() method determines whether a string includes a particular character or substring. It returns true if the character is included, otherwise the method returns false. There are additional parameters that can modify the comparison rules.

Syntax

// Determines whether the String includes a given character
String.Contains(char);

// Determines whether the String includes a given string
String.Contains(string);

// Determines whether the String includes a given character considering the type of comparison
String.Contains(char, comparisonType)

// Determines whether the String includes a given string considering the type of comparison
String.Contains(string, comparisonType)

.Contains() takes the following arguments:

• char is a single character.
• string is a sequence of characters.
• comparisonType is an enumeration value that allows to add specific rules to compare strings such as culture, case, and sort. Passing as an additional argument:
  • CurrentCulture determines whether strings match culture-sensitive criteria using the current system culture for comparison.
  • CurrentCultureIgnoreCase does the same as above and ignores the case.
  • InvariantCulture determines whether strings match using a fixed, culture-independent set of rules that remain consistent across all systems and regions.
  • InvariantCultureIgnoreCase does the same as above and ignores the case.
  • Ordinal determines whether strings match using binary sort rules. This is the fastest comparison method, performing a simple byte-by-byte comparison of Unicode values.
  • OrdinalIgnoreCase does the same as above and ignores the case.

Example

The following example shows how we can use .Contains() method

using System;

public class Example
{
    public static void Main()
    {
        string stringToSeek = "The distance is nothing when one has a motive.";
        string substring = "motive";
        char character = 'l';

        bool result;

        // String.Contains(string)
        result = stringToSeek.Contains(substring);
        Console.WriteLine(result);

        // String.Contains(char)
        result = stringToSeek.Contains(character);
        Console.WriteLine(result);
    }
}

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Here is the following output:

True
False

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Now, let’s see how we can use the comparisonType parameter to modify the comparison rules:

using System;
using System.Globalization;

public class Example
{
  public static void Main()
  {
    // Turkish culture handles 'i' and 'İ' differently
    CultureInfo turkishCulture = new CultureInfo("tr-TR");
    string turkishString = "İstanbul";
    string searchText = "istanbul";

    // Default culture comparison (typically en-US)
    bool defaultResult = turkishString.Contains(searchText, StringComparison.CurrentCultureIgnoreCase);

    // Turkish culture comparison
    CultureInfo.CurrentCulture = turkishCulture;
    bool turkishResult = turkishString.Contains(searchText,
      StringComparison.CurrentCultureIgnoreCase);

    Console.WriteLine($"Default culture result: {defaultResult}");
    Console.WriteLine($"Turkish culture result: {turkishResult}");
  }
}

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Here is the output:

Default culture result: True
Turkish culture result: False

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Codebyte Example

The example below determines whether the word helpful is included in the particular string.

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