Item duplication problem

Question

Hi friends,

My goal is to add a insert new value to a column where my column values are as follows

100 * 100
150 * 150
200 * 200
200 * 200

I get the following error:

Item has already been added. Key in dictionary: '200 x 200' Key being added: '200 x 200'

For next code:

SortedList sortedList = new SortedList();

foreach (ListItem listItem in ddldimension.Items)
    sortedList.Add(listItem.Text, listItem.Value);

if (!sortedList.ContainsKey(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension1")))
    sortedList.Add(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension1"), "defaultEmbedDimension1");

if (!sortedList.ContainsKey(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension2")))
    sortedList.Add(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension2"), "defaultEmbedDimension2");

if (!sortedList.ContainsKey(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension3")))
    sortedList.Add(CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension3"), "defaultEmbedDimension3");

Answer 1

From the error message you're getting, and from the documentation for SortedList:

In either case, a SortedList does not allow duplicate keys.

So it would appear that a SortedList isn't the right structure for you to be using in your application. Unfortunately, you've provided insufficient information to allow me to suggest something better.

Answer 2

SortedList does not allow adding duplicate keys. Use List<> (along with KeyValuePair for example) instead (eg. List<KeyValuePair<string, object>>).

Here is the solution for your code:

var list = new List<KeyValuePair<string, string>>();

foreach (var item in ddldimension.Items)
{
 list.Add(new KeyValuePair<string, string>(item.Text, item.Value));
}

var defaultEmbedDimension1 = CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension1");
int index = list.FindIndex(k => k.Key == defaultEmbedDimension1); // If there is no such Key, it will be -1. If you want to find by Value, replace k.Key by k.Value
if (index >= 0)
{
 list.Add(new KeyValuePair<string, string>(defaultEmbedDimension1, "defaultEmbedDimension1"));
}

In this way, you allow to keep duplicate keys in your structure. Note you invoke the same method twice. Initialize variable instead:

string defaultEmbedDimension1 = CommonUtilities.GetCustomString("DefaultValues", "defaultEmbedDimension1");

To populate list, you can alternatively use LINQ:

var list = ddldimensions.Items.Select(item => new KeyValuePair<string, string>(item.Text, item.Value)).ToList();

Read also: C# KeyValuePair Collection Hints at Dot Net Perls.

But if you decide to disallow duplicates and gently deal with them in SortedList, you can create an extension:

public static class SortedListExtensions
{
 public static bool AddIfNotContains<K, V>(this IDictionary<K, V> dictionary, K key, V value)
 {
  if (!dictionary.ContainsKey(key))
  {
   dictionary.Add(key, value);
   return true;
  }
  return false;
 }
}

And use it as I did below, without throwing exception:

var sortedList = new SortedList<string, string>();
sortedList.Add("a", "b");
sortedList.AddIfNotContains("a", "b"); // Will not be added
sortedList.AddIfNotContains("b", "b"); // Will be added