C# | Getting index of the specified value in a SortedList object

SortedList.IndexOfValue(Object) Method is used to get the zero-based index of the first occurrence of the specified value in a SortedList object.

Syntax:

public virtual int IndexOfValue (object value);

Here, value is the Value which is to be located in the SortedList object. The value can be null.

Return Value: This method return the zero-based index of the first occurrence of the value parameter, if the value is found in the SortedList object otherwise it returns -1.

Below programs illustrate the use of above-discussed method:

Example 1:

// C# code to get the zero-based index
// of the first occurrence of the specified
// value in a SortedList object
using System;
using System.Collections;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Creating a SortedList of integers
        SortedList mylist = new SortedList();

        // Adding elements to SortedList
        mylist.Add("First", "Ram");
        mylist.Add("Second", "Rohit");
        mylist.Add("Third", "Mohit");

        //taking value "Rohit" twice
        // but it give the first occurrence
        mylist.Add("Fourth", "Rohit");

        mylist.Add("Fifth", "Manish");


        // printing the keys and values of mylist
        Console.WriteLine("Index \t\t Keys \t\tValues");

        for (int i = 0; i < mylist.Count; i++)
        {
            Console.WriteLine("[{0}]\t\t{1}\t\t{2}", i,
                mylist.GetKey(i), mylist.GetByIndex(i));
        }

        Console.Write("\nThe index of value 'Rohit' is: ");

        // getting the index of value "Rohit"
        Console.Write(mylist.IndexOfValue("Rohit"));

        // getting the index of value which is
        // not present in mylist so it will
        // return -1
        Console.Write("\nThe index of value 'Kirti' is: ");
        Console.Write(mylist.IndexOfValue("Kirti"));
    }
}

Output:

Index          Keys         Values
[0]        Fifth        Manish
[1]        First        Ram
[2]        Fourth        Rohit
[3]        Second        Shyam
[4]        Third        Mohit

The index of value 'Rohit' is: 2
The index of value 'Kirti' is: -1

Example 2:

// C# code to get the  zero-based index
// of the first occurrence of the specified
// value in a SortedList object
using System;
using System.Collections;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Creating a SortedList of integers
        SortedList mylist = new SortedList();

        // Adding elements to SortedList
        mylist.Add("1", "C++");
        mylist.Add("2", "Java");
        mylist.Add("3", "DSA");

        // taking a value null
        mylist.Add("4", null);

        mylist.Add("5", "C#");


        // printing the keys and values of mylist
        Console.WriteLine("Index \t\t Keys \t\tValues");

        for (int i = 0; i < mylist.Count; i++)
        {
            Console.WriteLine("[{0}]\t\t{1}\t\t{2}", i,
                mylist.GetKey(i), mylist.GetByIndex(i));
        }

        Console.Write("\nThe index of value 'null' is: ");

        // getting the index of value "null"
        // it will give ArgumentNullException
        Console.Write(mylist.IndexOfValue(null));
    }
}

Output:

Index          Keys         Values
[0]        1        C++
[1]        2        Java
[2]        3        DSA
[3]        4        
[4]        5        C#

The index of value 'null' is: 3

Note:

• The index sequence is based on the sort sequence. When an element is added, it is inserted into SortedList in the correct sort order, and the indexing adjusts accordingly. When an element is removed, the indexing also adjusts accordingly. So, the index of a specific key/value pair may change.
• The values of the elements of the SortedList are compared to the specified value using the Equals method.
• This method uses a linear search; therefore, this method is an O(n) operation, where n is Count.

Reference:

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