C# | Search in a SortedList object

Last Updated : 11 Oct, 2018

SortedList class is a collection of (key, value) pairs which are sorted according to keys. Those pairs can be accessible by key and as well as by index(zero-based indexing). This comes under System.Collections namespace. SortedList.ContainsKey(Object) method is used to check whether a SortedList object contains a specific key or not.

Properties:

A SortedList element can be accessed by its key or by its index.
A SortedList object internally maintains two arrays to store the elements of the list, i.e, one array for the keys and another array for the associated values.
A key cannot be null, but a value can be.
The capacity of a SortedList object is the number of elements the SortedList can hold.
A SortedList does not allow duplicate keys.
Operations on a SortedList object tend to be slower than operations on a Hashtable object because of the sorting.
Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

Syntax:

  public virtual bool ContainsKey (object key);

Here, key is the key to locate in the SortedList object.

Return Value: This method will return True if the SortedList object contains an element with the specified key otherwise it returns False.

Exceptions:

ArgumentNullException : If the key is null.
InvalidOperationException : If the comparer throws an exception.

Below given are some examples to understand the implementation in a better way:

Example 1:

   // C# code to check if a SortedList 
// object contains a specific key 
using System; 
using System.Collections; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating an SortedList 
        SortedList mySortedList = new SortedList(); 
  
        // Adding elements to SortedList 
        mySortedList.Add("h", "Hello"); 
        mySortedList.Add("g", "Geeks"); 
        mySortedList.Add("f", "For"); 
        mySortedList.Add("n", "Noida"); 
  
        // Checking if a SortedList object 
        // contains a specific key 
        Console.WriteLine(mySortedList.ContainsKey("g")); 
    } 
} 
 
  

Output:

  True

Example 2:

   // C# code to check if a SortedList 
// object contains a specific key 
using System; 
using System.Collections; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating an SortedList 
        SortedList mySortedList = new SortedList(); 
  
        // Adding elements to SortedList 
        mySortedList.Add("h", "Hello"); 
        mySortedList.Add("g", "Geeks"); 
        mySortedList.Add("f", "For"); 
        mySortedList.Add("n", "Noida"); 
  
        // Checking if a SortedList object 
        // contains a specific key 
        // It should throw ArgumentNullException 
        // as the Key can not be null 
        Console.WriteLine(mySortedList.ContainsKey(null)); 
    } 
} 
 
  

Error:

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

Note: This method uses a binary search algorithm, therefore, this method is an O(log n) operation, where n is Count.

Reference:

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

C# | Getting the keys in a SortedList object

Sahil_Bansall

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C# | Search in a SortedList object

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