Map.ContainsKey<'Key,'Value> Method (F#)

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Tests if an element is in the domain of the map.

Namespace/Module Path: Microsoft.FSharp.Collections

Assembly: FSharp.Core (in FSharp.Core.dll)

// Signature:
member this.ContainsKey : 'Key -> bool (requires comparison)

// Usage:
map.ContainsKey (key)

Parameters

  • key
    Type: 'Key

    The input key.

Return Value

true if the map contains the given key.

Example

The following code shows how to use the ContainsKey method.

let map1 = Map.ofList [ (1, "one"); (2, "two"); (3, "three") ]
let findKeyAndPrint key (map : Map<int,string>) =
    if (map.ContainsKey key) then
        printfn "The specified map contains the key %d." key
    else
        printfn "The specified map does not contain the key %d." key
findKeyAndPrint 1 map1
findKeyAndPrint 0 map1

Output

The specified map contains the key 1.
The specified map does not contain the key 0.

Platforms

Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

Version Information

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

See Also

Reference

Collections.Map<'Key,'Value> Class (F#)

Microsoft.FSharp.Collections Namespace (F#)