How to Check if a Value Exists in a Dictionary in C#

How to Check if a Value Exists in a Dictionary in C# ?

Answer

To check if a value exists in a dictionary in C#, you can use the `ContainsValue` method of the `Dictionary` class from the `System.Collections.Generic` namespace.

✐ Examples

1 Checking if a Value Exists Using the `ContainsValue` Method

We can check if a value exists in a dictionary in C# using the `ContainsValue` method. This example demonstrates how to check for the presence of a value and print a message based on the result.

For example,

We start by including the necessary namespace: using System.Collections.Generic;.
We declare and initialize a dictionary named myDictionary with integer keys and string values.
We use the `ContainsValue` method to check if a value exists in the dictionary.
We print a message based on whether the value exists or not.

C# Program

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Declare and initialize a dictionary
        Dictionary<int, string> myDictionary = new Dictionary<int, string>
        {
            {1, "One"},
            {2, "Two"},
            {3, "Three"}
        };

        // Value to check
        string valueToCheck = "Two";

        // Check if the value exists using the ContainsValue method
        if (myDictionary.ContainsValue(valueToCheck))
        {
            Console.WriteLine("Value '{0}' exists in the dictionary.", valueToCheck);
        }
        else
        {
            Console.WriteLine("Value '{0}' does not exist in the dictionary.", valueToCheck);
        }
    }
}

Output

Value 'Two' exists in the dictionary.

2 Checking if a Value Does Not Exist Using the `ContainsValue` Method

We can check if a value does not exist in a dictionary in C# using the `ContainsValue` method. This example demonstrates how to check for the absence of a value and print a message based on the result.

For example,

We start by including the necessary namespace: using System.Collections.Generic;.
We declare and initialize a dictionary named myDictionary with integer keys and string values.
We use the `ContainsValue` method to check if a value does not exist in the dictionary.
We print a message based on whether the value exists or not.

C# Program

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Declare and initialize a dictionary
        Dictionary<int, string> myDictionary = new Dictionary<int, string>
        {
            {1, "One"},
            {2, "Two"},
            {3, "Three"}
        };

        // Value to check
        string valueToCheck = "Four";

        // Check if the value does not exist using the ContainsValue method
        if (!myDictionary.ContainsValue(valueToCheck))
        {
            Console.WriteLine("Value '{0}' does not exist in the dictionary.", valueToCheck);
        }
        else
        {
            Console.WriteLine("Value '{0}' exists in the dictionary.", valueToCheck);
        }
    }
}

Output

Value 'Four' does not exist in the dictionary.

Summary

In this tutorial, we learned How to Check if a Value Exists in a Dictionary in C# language with well detailed examples.

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How to Check if a Value Exists in a Dictionary in C#