Use the Remove() method to remove a key from SortedList : SortedList « Data Structure « C# / CSharp Tutorial

using System;
using System.Collections;

class MainClass
{

  public static void Main()
  {
    SortedList mySortedList = new SortedList();

    mySortedList.Add("NY", "New York");
    mySortedList.Add("FL", "Florida");
    mySortedList.Add("AL", "Alabama");
    mySortedList.Add("WY", "Wyoming");
    mySortedList.Add("CA", "California");

    foreach (string myKey in mySortedList.Keys)
    {
      Console.WriteLine("myKey = " + myKey);
    }

    foreach(string myValue in mySortedList.Values)
    {
      Console.WriteLine("myValue = " + myValue);
    }
    
    Console.WriteLine("Removing FL from mySortedList");
    mySortedList.Remove("FL");
  }
}

myKey = AL
myKey = CA
myKey = FL
myKey = NY
myKey = WY
myValue = Alabama
myValue = California
myValue = Florida
myValue = New York
myValue = Wyoming
Removing FL from mySortedList

11.33.SortedList
	11.33.1.	Create a SortedList using the default comparer
	11.33.2.	Create a SortedList using the specified case-insensitive comparer
	11.33.3.	Create a SortedList using the specified CaseInsensitiveComparer, which is based on the Turkish culture (tr-TR)
	11.33.4.	Create a SortedList using the StringComparer.InvariantCultureIgnoreCase value
	11.33.5.	Add value to SortedList and get contents by integer indexes
	11.33.6.	Add element to SortedList by using the indexer.
	11.33.7.	Show integer indexes of entries
	11.33.8.	Get value by key indexer
	11.33.9.	Use the ContainsValue() method to check if mySortedList contains a value
	11.33.10.	Use the Remove() method to remove a key from SortedList
	11.33.11.	Get the key at index 3 using the GetKey() method
	11.33.12.	Get the index of the element with a key using the IndexOfKey() method
	11.33.13.	Get the index of the element with a value using the IndexOfValue() method
	11.33.14.	Get the key list using the GetKeyList() method
	11.33.15.	Get the value list using the GetValueList() method