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/**

* @name Inefficient use of ContainsKey

* @description Testing whether a dictionary contains a value before getting it is inefficient and redundant.

* Use 'TryGetValue' to combine these two steps.

* @kind problem

* @problem.severity recommendation

* @precision high

* @id cs/inefficient-containskey

* @tags quality

* reliability

* performance

import csharp

import semmle.code.csharp.commons.StructuralComparison

import semmle.code.csharp.controlflow.Guards as G

pragma[noinline]

private predicate candidate(MethodCall mc, IndexerRead access) {

mc.getTarget().hasName("ContainsKey") and

access.getQualifier().(G::GuardedExpr).isGuardedBy(mc, mc.getQualifier(), _)

}

from MethodCall call, IndexerRead index

where

candidate(call, index) and

sameGvn(call.getArgument(0), index.getIndex(0))

select call, "Inefficient use of 'ContainsKey' and $@.", index, "indexer"