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

Den Delimarsky|Last Updated: 8/18/2017
1 Contributor

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)


key Type: 'Key

The input key.

Return Value

true if the map contains the given key.


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
        printfn "The specified map does not contain the key %d." key
findKeyAndPrint 1 map1
findKeyAndPrint 0 map1


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


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

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

Microsoft.FSharp.Collections Namespace (F#)

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