Check out example codes for "how to show a first item in a combobox in c# winforms". It will help you in understanding the concepts better.

Code Example 1

comboBox1.SelectedItem = "your value"; //

Code Example 2

var item = ChunkList.SingleOrDefault(x => x.UniqueId == ChunkID);
if (item != null)
    ChunkList.Remove(item);

Code Example 3

myList.Where(sublist => sublist.Any(item => item.Name == "ABC" && item.Action == "123"));

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