C# | Check if the StringDictionary contains a specific key
StringDictionary.ContainsKey(String) method is used to check whether the StringDictionary contains a specific key or not.
Syntax:
public virtual bool ContainsKey (string key);
Here, key is the key to locate in the StringDictionary.
Return Value: This method returns true if the StringDictionary contains an entry with the specified key, otherwise it returns the false.
Exception: This method will give ArgumentNullException if the key is null.
Below programs illustrate the use of StringDictionary.ContainsKey(String) method:
Example 1:
// C# code to check if the // StringDictionary contains // a specific key using System; using System.Collections; using System.Collections.Specialized; class GFG { // Driver code public static void Main() { // Creating a StringDictionary named myDict StringDictionary myDict = new StringDictionary(); // Adding key and value into the StringDictionary myDict.Add( "G" , "Beginner" ); myDict.Add( "F" , "For" ); myDict.Add( "C" , "C++" ); myDict.Add( "DS" , "Data Structures" ); myDict.Add( "N" , "Noida" ); // Checking if "DS" is contained in // StringDictionary myDict if (myDict.ContainsKey( "DS" )) Console.WriteLine( "StringDictionary myDict contains the key" ); else Console.WriteLine( "StringDictionary myDict does not contain the key" ); } } |
Output:
StringDictionary myDict contains the key
Example 2:
// C# code to check if the // StringDictionary contains // a specific key using System; using System.Collections; using System.Collections.Specialized; class GFG { // Driver code public static void Main() { // Creating a StringDictionary named myDict StringDictionary myDict = new StringDictionary(); // Adding key and value into the StringDictionary myDict.Add( "G" , "Beginner" ); myDict.Add( "F" , "For" ); myDict.Add( "C" , "C++" ); myDict.Add( "DS" , "Data Structures" ); myDict.Add( "N" , "Noida" ); // Checking if "null" is contained in // StringDictionary myDict // This should raise "ArgumentNullException" // as the key is null if (myDict.ContainsKey( null )) Console.WriteLine( "StringDictionary myDict contains the key" ); else Console.WriteLine( "StringDictionary myDict does not contain the key" ); } } |
Runtime Error:
Unhandled Exception:
System.ArgumentNullException: Value cannot be null.
Parameter name: key
Note:
- The key is handled in a case-insensitive manner i.e, it is translated to lowercase before it is added to the string dictionary.
- This method is an O(1) operation.
Reference:
- https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.stringdictionary.containskey?view=netframework-4.7.2
Contact Us