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Posted 22 Apr 2008
Licenced CPOL

Looking up items in HashTable/Dictionary objects that have multiple keys

, 1 May 2008
Dictionary objects take a single key as a look up key. This class simplifies using a Dictionary when you have multiple keys, such as two strings and an int, etc.
using System;
using System.Collections.Generic;
using System.Text;

using NUnit.Framework;
using Utility;
using System.Diagnostics;

namespace Testing
    public class TestStringDictionaryOnly
        /// <summary>
        /// Define test class to use key for
        /// </summary>
        public class TestClass
            public string Column1 = null;
            public string Column2 = null;

            public TestClass(string Column1, string Column2)
                this.Column1 = Column1;
                this.Column2 = Column2;

        //null keys are a problem that would have to be thought about on every usage
        //dictionary objects need to be created for each additional key

        public class PerfResults { public long initMS; public long lookupMS; }

        private string GetTestClassKey(TestClass testClass)
            return testClass.Column1 + "~" + testClass.Column2;

        public PerfResults GetTestPerf()
            Dictionary<string, TestClass> testLookups = new Dictionary<string, TestClass>();
            Stopwatch stopWatch = new Stopwatch();
            PerfResults results = new PerfResults();

            //test initialization
            for (int i = 0; i < 1000000; i++)
                TestClass testClass = new TestClass("Column1-" + i, "Column2-" + i);
                testLookups.Add(GetTestClassKey(testClass), testClass);

            results.initMS = stopWatch.ElapsedMilliseconds;

            //test getting
            stopWatch = new Stopwatch();
            for (int i = 0; i < 1000000; i++)
                TestClass testClass = new TestClass("Column1-" + i, "Column2-" + i);
                if (!testLookups.ContainsKey(GetTestClassKey(testClass)))
                    throw new ArgumentException("Can't find object we know is there");

            results.lookupMS = stopWatch.ElapsedMilliseconds;

            return results;

        public void TestPerf()
            int testRuns = 10;
            PerfResults totalResults = new PerfResults();

            for (int i = 0; i < testRuns; i++)
                PerfResults thisResult = GetTestPerf();
                totalResults.initMS += thisResult.initMS;
                totalResults.lookupMS += thisResult.lookupMS;

            Debug.WriteLine("Initialization: " + (totalResults.initMS / testRuns).ToString("N0") + "ms");
            Debug.WriteLine("Lookups: " + (totalResults.lookupMS / testRuns).ToString("N0") + "ms");


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About the Author

Paul B.
United States United States
I've been a software developer since 1996 and have enjoyed C# since 2003. I have a Bachelor's degree in Computer Science and for some reason, a Master's degree in Business Administration. I currently do software development contracting/consulting.

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