CacheKey.Equals(object) override can return true when the parameters have the 
same HashCode but are not equal.
--------------------------------------------------------------------------------------------------------------

         Key: IBATISNET-118
         URL: http://issues.apache.org/jira/browse/IBATISNET-118
     Project: iBatis for .NET
        Type: Bug
  Components: DataMapper  
    Versions: DataMapper 1.2.1    
 Environment: Windows
    Reporter: Thomas Tannahill


CacheKey.Equals(object) override can return true when the parameters have the 
same HashCode but are not equal.  This can cause false cache hits.

Only an issue for complex parameters.

Failing NUnit test:

---- UNIT TEST BEGIN ----
using IBatisNet.DataMapper;
using IBatisNet.DataMapper.TypeHandlers;
using NUnit.Framework;

namespace IBatisNet.DataAccess
{
        [TestFixture]
        public class CacheKeyTests
        {
                private const long A_LONG = 1L;
                private const long ANOTHER_LONG_WITH_SAME_HASHCODE = 
-9223372034707292159;
                
                public CacheKeyTests()
                {
                }

                [Test]
                public void 
ShouldNotBeConsideredEqualWhenParametersHaveTheSameHashCodeButAreNotEqual()
                {
                        TypeHandlerFactory factory = new TypeHandlerFactory(); 

                        // Two cache keys are equal except for the parameter.
                        CacheKey key = new CacheKey(factory, "STATEMENT", 
"SQL", new TestClass(A_LONG), new string[] {"AProperty"}, 0, 0, 
CacheKeyType.Object);
                        CacheKey aDifferentKey = new CacheKey(factory, 
"STATEMENT", "SQL", new TestClass(ANOTHER_LONG_WITH_SAME_HASHCODE), new 
string[] {"AProperty"}, 0, 0, CacheKeyType.Object);

                        Assert.IsFalse(aDifferentKey.Equals(key)); // should 
not be equal.
                }
        }

        public class TestClass
        {
                private long aProperty;

                public TestClass(long aProperty)
                {
                        this.aProperty = aProperty;
                }

                public long AProperty
                {
                        get { return aProperty; }
                        set { aProperty = value; }
                }
        }
}
---- UNIT TEST END ----

The test passes if you replace this line in CacheKey.Equals():

               if (_hashCode != cacheKey._hashCode) return false;

with something like this:

               if (this._parameter == null && cacheKey._parameter != null) 
return false;
               if (this._parameter != null && cacheKey._parameter == null) 
return false;
               if (!this._parameter.Equals(cacheKey._parameter)) return false;


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