C# | Check the HybridDictionary for a specific key

HybridDictionary.Contains(Object) method is used to determine whether the HybridDictionary contains a specific key or not.

Syntax:

public bool Contains (object key);

Here, key is the key to locate in the HybridDictionary.

Return Value: This method will return True if the HybridDictionary contains an entry with the specified key, otherwise, False.

Exception: The method throws ArgumentNullException if the key is null.

Below are the programs to illustrate the use of HybridDictionary.Contains(Object) method:

Example 1:

// C# code to check whether the
// HybridDictionary contains a specific key.
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();

        // Adding key/value pairs in myDict
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
        myDict.Add("E", "Elephant");
        myDict.Add("F", "Fish");

        // To check whether the HybridDictionary
        // contains "G".
        Console.WriteLine(myDict.Contains("G"));

        // To check whether the HybridDictionary
        // contains "B".
        Console.WriteLine(myDict.Contains("B"));
    }
}

Output:

False
True

Example 2:

// C# code to check whether the
// HybridDictionary contains a specific key.
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();

        // Adding key/value pairs in myDict
        myDict.Add("I", "first");
        myDict.Add("II", "second");
        myDict.Add("III", "third");
        myDict.Add("IV", "fourth");
        myDict.Add("V", "fifth");

        // To check whether the HybridDictionary
        // contains "null". This should raise
        // "ArgumentNullException" as key is null
        Console.WriteLine(myDict.Contains(null));
    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentNullException: Key cannot be null.
Parameter name: key

Note: This method is an O(1) operation.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.hybriddictionary.contains?view=netframework-4.7.2