Make a dictionary with List<string>
as value, and then just add values :
foreach(var d in c)
{
if (!dict.ContainsKey(d.Key))
dict.Add(d.Key, new List<string>());
dict[d.Key].Add(d.Value);
}
and later you can get comma delimited string from list with string.Join
string commaDelimitedList = string.Join(",", valueList.ToArray());
solved Dictionary one key many values in code c#