Why is my dictionary data being overwritten?

Question

not sure what is going on here. My data items I store in the first dictionary entry get overwritten when I go to update data to the second entry. The dictionary's first entry is acting like it is using a reference to the original object so when i change it all instances in the dictionary change. the first set of data is 1,2,3 and stored in partitionInfo[0]. when i got to store the next set of data, 4,5,6 partitionInfo[1] updates but parttionInfo[0] updates those values as well. so i end up with my two dictionary entries have the same set of data. however the strings stay unique. representation code of what i am seeing

private void button1_Click(object sender, EventArgs e) { Datum dataItems = new Datum(); Partition partitionItem = new Partition(); LRU lruItem = new LRU(); dataItems.minData = "1"; dataItems.maxData = "2"; dataItems.avgData = "3"; partitionItem.partitionInfo.Add("Entry1", dataItems); dataItems.minData = "4"; dataItems.maxData = "5"; dataItems.avgData = "6"; partitionItem.partitionInfo.Add("Entry2", dataItems); lruItem.lruInfo.Add("Parent", partitionItem); } public class LRU { public Dictionary<string, Partition> lruInfo = new Dictionary<string, Partition>(); } public class Partition { public Dictionary<string, Datum> partitionInfo = new Dictionary<string, Datum>(); } public class Datum { public string minData; public string maxData; public string avgData; }

Lee Taylor · Accepted Answer · 2022-05-18 23:21:00Z

You are overwriting your values beginning with the line dataItems.minData = "4"; Just because you've stored the value in Entry1 it doesn't "lock it away" as I suspect you think.

You original comment:

The dictionary's first entry is acting like it is using a reference to the original object so when I change it all instances in the dictionary change

You were close to grasping the error in your code...

See the fixed code:

Partition partitionItem = new Partition(); Datum dataItems = new Datum(); // **** It's better to declare your variables just // before you use them to make it clearer **** dataItems.minData = "1"; dataItems.maxData = "2"; dataItems.avgData = "3"; partitionItem.partitionInfo.Add("Entry1", dataItems); dataItems = new Datum(); // **** ADDED LINE **** // We now have a new block of memory containing a `Datum` // the one above is left untouched dataItems.minData = "4"; dataItems.maxData = "5"; dataItems.avgData = "6"; partitionItem.partitionInfo.Add("Entry2", dataItems); LRU lruItem = new LRU(); **** Moved, as before **** lruItem.lruInfo.Add("Parent", partitionItem);

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