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Comparing Hashtables

Posted on 2003-10-23
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Last Modified: 2012-05-04
Does anyone know how to compare two hashtables?

Hashtable ht1 = new Hashtable();
ht1.Add( "exampleKey", "exampleValue" );

Hashtable ht2 = new Hashtable();
ht2.Add( "exampleKey", "exampleValue" );

// This returns false
ht1.Equals( ht2 );
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Question by:chadboyer
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5 Comments
 
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Expert Comment

by:vo1d
ID: 9609713
it depends on what you wanna compare.
if you wann check if they are euqal you can check if the dimensions are the same at first.
if the dimensions are the same, you can doublecheck the specific elements to each other.
do you mean that?
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Author Comment

by:chadboyer
ID: 9609873
I want to compare the dimensions and the elements.  I was just hoping that ht1.Equals( ht2 ) would do the work for me.  But it doesn't.
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LVL 22

Accepted Solution

by:
_TAD_ earned 125 total points
ID: 9609957


ht1.Equals(ht2) checks to see if the ht1 and ht2 variables refer to the same object.


Hastable ht1 = new Hashtabl();
...
..    Fill Hashtable
.

Hashtable ht2 = ht1;

ht1.Equals(ht2)   //  TRUE


This is because ht1 and ht2 really are the same object


Hastable ht1 = new Hashtabl();
Hastable ht2 = new Hashtabl();
ht1.Equals(ht2) // FALSE

you have two distinct objects here ( two "new" statements means two unique obects)


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Author Comment

by:chadboyer
ID: 9610030
I wrote my own Hashtable compare function.  Thanks anyway...
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LVL 22

Expert Comment

by:_TAD_
ID: 9610174


here is some code to compare hashtable values and keys



                  Hashtable ht1 = new Hashtable();

                  ht1.Add("1","one");
                  ht1.Add("2","two");
                  ht1.Add("3","three");
                  ht1.Add("4","four");


                  Hashtable ht2 = new Hashtable();

                  ht2.Add("1","one");
                  ht2.Add("2","two");
                  ht2.Add("3","three");
                  ht2.Add("4","four");

                  IDictionaryEnumerator myEnum = ht1.GetEnumerator();
            
                  bool isSame = true;

                  while ( myEnum.MoveNext() )
                        if (ht2.ContainsKey(myEnum.Key))
                        {
                              if (ht1[myEnum.Key]!=ht2[myEnum.Key])
                              {
                                    isSame = false;
                                    break;
                              }                              
                        }
                        else
                        {
                              isSame = false;
                              break;
                        }

                  Console.WriteLine("Hashtables ht1 & ht2 are {0}the same", (isSame)?"":"NOT ");
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