Question

I want to add items to a dictionary that contains a dictionary within please refer the code below.

Dictionary<string, Dictionary<string, int>> dict = new Dictionary<string, Dictionary<string, int>>();
foreach (var item in TrainingCourseList)
{
    // I have to add item.ID,item.Name,item.Score something like below
    dict.Add(item.ID,item.Name,item.Score);
}

Answer 1

I guess Tuple<string, string, int> is the best suit for your case, not Dictionary:

var list = TrainingCourseList
    .Select(item => Tuple.Create(item.ID, item.Name, item.Score));