Remove entry with specified key from the StringDictionary in C#

The StringDictionary class in C# provides the Remove() method to delete entries with a specified key. This method removes both the key and its associated value from the collection. StringDictionary is case-insensitive, meaning keys are automatically converted to lowercase.

Syntax

Following is the syntax for the Remove() method −

public virtual void Remove(string key)

Parameters

• key − The string key to remove from the StringDictionary.

Using Remove() Method

Example

using System;
using System.Collections;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringDictionary strDict1 = new StringDictionary();
      strDict1.Add("A", "John");
      strDict1.Add("B", "Andy");
      strDict1.Add("C", "Tim");
      strDict1.Add("D", "Ryan");
      strDict1.Add("E", "Kevin");
      strDict1.Add("F", "Katie");
      strDict1.Add("G", "Brad");
      Console.WriteLine("StringDictionary1 key-value pairs...");
      foreach(DictionaryEntry de in strDict1) {
         Console.WriteLine(de.Key + " " + de.Value);
      }
      strDict1.Remove("D");
      Console.WriteLine("\nStringDictionary1 key-value pairs after removing a key...");
      foreach(DictionaryEntry de in strDict1) {
         Console.WriteLine(de.Key + " " + de.Value);
      }
      StringDictionary strDict2 = new StringDictionary();
      strDict2.Add("1", "A");
      strDict2.Add("2", "B");
      strDict2.Add("3", "C");
      strDict2.Add("4", "D");
      strDict2.Add("5", "E");
      Console.WriteLine("\nStringDictionary2 key-value pairs...");
      IEnumerator demoEnum = strDict2.GetEnumerator();
      DictionaryEntry d;
      while (demoEnum.MoveNext()) {
         d = (DictionaryEntry)demoEnum.Current;
         Console.WriteLine("Key = " + d.Key + ", Value = " + d.Value);
      }
   }
}

The output of the above code is −

StringDictionary1 key-value pairs...
a John
b Andy
c Tim
d Ryan
e Kevin
f Katie
g Brad

StringDictionary1 key-value pairs after removing a key...
a John
b Andy
c Tim
e Kevin
f Katie
g Brad

StringDictionary2 key-value pairs...
Key = 1, Value = A
Key = 2, Value = B
Key = 3, Value = C
Key = 4, Value = D
Key = 5, Value = E

Removing Multiple Keys

Example

using System;
using System.Collections;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringDictionary strDict1 = new StringDictionary();
      strDict1.Add("A", "One");
      strDict1.Add("B", "Two");
      strDict1.Add("C", "Three");
      strDict1.Add("D", "Four");
      strDict1.Add("E", "Five");
      Console.WriteLine("StringDictionary1 key-value pairs...");
      foreach(DictionaryEntry de in strDict1) {
         Console.WriteLine(de.Key + " " + de.Value);
      }
      strDict1.Remove("B");
      strDict1.Remove("C");
      Console.WriteLine("\nStringDictionary1 key-value pairs after removing keys...");
      foreach(DictionaryEntry de in strDict1) {
         Console.WriteLine(de.Key + " " + de.Value);
      }
   }
}

The output of the above code is −

StringDictionary1 key-value pairs...
a One
b Two
c Three
d Four
e Five

StringDictionary1 key-value pairs after removing keys...
a One
d Four
e Five

Key Points

• The Remove() method is case-insensitive ? keys are converted to lowercase internally.

• If the specified key does not exist, the method does nothing and no exception is thrown.

• After removal, the Count property is decremented by one.

• Multiple keys can be removed by calling Remove() multiple times.

Conclusion

The Remove() method in StringDictionary provides an efficient way to delete key-value pairs by specifying the key. Remember that StringDictionary operations are case-insensitive, and removing non-existent keys does not raise exceptions.