Hashtable.ContainsValue Method
Assembly: mscorlib (in mscorlib.dll)
Parameters
- value
The value to locate in the Hashtable. The value can be a null reference (Nothing in Visual Basic).
Return Value
true if the Hashtable contains an element with the specified value; otherwise, false.The values of the elements of the Hashtable are compared to the specified value using the Object.Equals method.
This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.
Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.
The following example shows how to determine whether the Hashtable contains a specific element.
using System; using System.Collections; public class SamplesHashtable { public static void Main() { // Creates and initializes a new Hashtable. Hashtable myHT = new Hashtable(); myHT.Add( 0, "zero" ); myHT.Add( 1, "one" ); myHT.Add( 2, "two" ); myHT.Add( 3, "three" ); myHT.Add( 4, "four" ); // Displays the values of the Hashtable. Console.WriteLine( "The Hashtable contains the following values:" ); PrintIndexAndKeysAndValues( myHT ); // Searches for a specific key. int myKey = 2; Console.WriteLine( "The key \"{0}\" is {1}.", myKey, myHT.ContainsKey( myKey ) ? "in the Hashtable" : "NOT in the Hashtable" ); myKey = 6; Console.WriteLine( "The key \"{0}\" is {1}.", myKey, myHT.ContainsKey( myKey ) ? "in the Hashtable" : "NOT in the Hashtable" ); // Searches for a specific value. String myValue = "three"; Console.WriteLine( "The value \"{0}\" is {1}.", myValue, myHT.ContainsValue( myValue ) ? "in the Hashtable" : "NOT in the Hashtable" ); myValue = "nine"; Console.WriteLine( "The value \"{0}\" is {1}.", myValue, myHT.ContainsValue( myValue ) ? "in the Hashtable" : "NOT in the Hashtable" ); } public static void PrintIndexAndKeysAndValues( Hashtable myHT ) { int i = 0; Console.WriteLine( "\t-INDEX-\t-KEY-\t-VALUE-" ); foreach ( DictionaryEntry de in myHT ) Console.WriteLine( "\t[{0}]:\t{1}\t{2}", i++, de.Key, de.Value ); Console.WriteLine(); } } /* This code produces the following output. The Hashtable contains the following values: -INDEX- -KEY- -VALUE- [0]: 4 four [1]: 3 three [2]: 2 two [3]: 1 one [4]: 0 zero The key "2" is in the Hashtable. The key "6" is NOT in the Hashtable. The value "three" is in the Hashtable. The value "nine" is NOT in the Hashtable. */
import System.*;
import System.Collections.*;
public class SamplesHashtable
{
public static void main(String[] args)
{
// Creates and initializes a new Hashtable.
Hashtable myHT = new Hashtable();
myHT.Add(new Integer(0), "zero");
myHT.Add(new Integer(1), "one");
myHT.Add(new Integer(2), "two");
myHT.Add(new Integer(3), "three");
myHT.Add(new Integer(4), "four");
// Displays the values of the Hashtable.
Console.WriteLine("The Hashtable contains the following values:");
PrintIndexAndKeysAndValues(myHT);
// Searches for a specific key.
int myKey = 2;
Console.WriteLine("The key \"{0}\" is {1}.",
System.Convert.ToString(myKey),
(myHT.ContainsKey(new Integer(myKey))) ?
"in the Hashtable" : "NOT in the Hashtable");
myKey = 6;
Console.WriteLine("The key \"{0}\" is {1}.",
System.Convert.ToString(myKey),
(myHT.ContainsKey(new Integer(myKey))) ?
"in the Hashtable" : "NOT in the Hashtable");
// Searches for a specific value.
String myValue = "three";
Console.WriteLine("The value \"{0}\" is {1}.", myValue,
(myHT.ContainsValue(myValue)) ?
"in the Hashtable" : "NOT in the Hashtable");
myValue = "nine";
Console.WriteLine("The value \"{0}\" is {1}.", myValue,
(myHT.ContainsValue(myValue)) ?
"in the Hashtable" : "NOT in the Hashtable");
} //main
public static void PrintIndexAndKeysAndValues(Hashtable myHT)
{
int i = 0;
Console.WriteLine("\t-INDEX-\t-KEY-\t-VALUE-");
IEnumerator myEnumerator = myHT.GetEnumerator();
while (myEnumerator.MoveNext()) {
DictionaryEntry de = (DictionaryEntry)myEnumerator.get_Current();
Console.WriteLine("\t[{0}]:\t{1}\t{2}",
System.Convert.ToString(i++),
de.get_Key().toString(), de.get_Value().toString());
}
Console.WriteLine();
} //PrintIndexAndKeysAndValues
} //SamplesHashtable
/*
This code produces the following output.
The Hashtable contains the following values:
-INDEX- -KEY- -VALUE-
[0]: 4 four
[1]: 3 three
[2]: 2 two
[3]: 1 one
[4]: 0 zero
The key "2" is in the Hashtable.
The key "6" is NOT in the Hashtable.
The value "three" is in the Hashtable.
The value "nine" is NOT in the Hashtable.
*/
import System import System.Collections import Microsoft.VisualBasic // Creates and initializes a new Hashtable. var myHT : Hashtable = new Hashtable() myHT.Add(0, "zero") myHT.Add(1, "one") myHT.Add(2, "two") myHT.Add(3, "three") myHT.Add(4, "four") // Displays the values of the Hashtable. Console.WriteLine("The Hashtable contains the following values:") PrintIndexAndKeysAndValues(myHT) // Searches for a specific key. var msg : String var myKey : int = 2 if(myHT.ContainsKey(myKey)) msg = "in the Hashtable" else msg = "NOT in the Hashtable" Console.WriteLine("The key \"{0}\" is {1}.", myKey, msg) myKey = 6 if(myHT.ContainsKey(myKey)) msg = "in the Hashtable" else msg = "NOT in the Hashtable" Console.WriteLine("The key \"{0}\" is {1}.", myKey, msg) // Searches for a specific value. var myValue : String = "three" if(myHT.ContainsValue(myValue)) msg = "in the Hashtable" else msg = "NOT in the Hashtable" Console.WriteLine("The value \"{0}\" is {1}.", myValue, msg) myValue = "nine" if(myHT.ContainsValue(myValue)) msg = "in the Hashtable" else msg = "NOT in the Hashtable" Console.WriteLine("The value \"{0}\" is {1}.", myValue, msg) function PrintIndexAndKeysAndValues(myList : Hashtable){ var myEnumerator : IDictionaryEnumerator = myList.GetEnumerator() var i : int = 0 Console.WriteLine("\t-INDEX-\t-KEY-\t-VALUE-") while(myEnumerator.MoveNext()){ Console.WriteLine("\t[{0}]:\t{1}\t{2}", i++, myEnumerator.Key, myEnumerator.Value) } Console.WriteLine() } // This code produces the following output. // // The Hashtable contains the following values: // -INDEX- -KEY- -VALUE- // [0]: 4 four // [1]: 3 three // [2]: 2 two // [3]: 1 one // [4]: 0 zero // // The key "2" is in the Hashtable. // The key "6" is NOT in the Hashtable. // The value "three" is in the Hashtable. // The value "nine" is NOT in the Hashtable.
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.