C# | Check whether a Hashtable contains a specific key or not
Last Updated :
01 Feb, 2019
Hashtable.Contains(Object) Method is used to check whether the Hashtable contains a specific key or not.
Syntax:
public virtual bool Contains (object key);
Here, key is the Key of Object type which is to be located in the Hashtable.
Return Value: This method returns true if the Hashtable contains an element with the specified key otherwise returns false.
Exception: This method will give ArgumentNullException if the key is null.
Note:
- Hashtable.ContainsKey(Object) Method is also used to check whether the Hashtable contains a specific key or not. This method behaves same as Contains() method.
- Contains method implements IDictionary.Contains. It behaves exactly as ContainsKey and this method is an O(1) operation.
Below programs illustrate the use of above-discussed method:
Example 1:
using System;
using System.Collections;
class GFG {
public static void Main()
{
Hashtable myTable = new Hashtable();
myTable.Add( "g" , "geeks" );
myTable.Add( "c" , "c++" );
myTable.Add( "d" , "data structures" );
myTable.Add( "q" , "quiz" );
Console.WriteLine(myTable.Contains( "d" ));
}
}
|
Output:
True
Example 2:
using System;
using System.Collections;
class GFG {
public static void Main()
{
Hashtable myTable = new Hashtable();
myTable.Add( "1" , "C" );
myTable.Add( "2" , "C++" );
myTable.Add( "3" , "Java" );
myTable.Add( "4" , "Python" );
Console.WriteLine(myTable.Contains( null ));
}
}
|
Runtime Error:
Unhandled Exception:
System.ArgumentNullException: Key cannot be null.
Parameter name: key
Reference:
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