How to get value of SelectedValue in ComboBox filled with Dictionary

Looks like you have to cast SelectedValue into KeyValuePair<int, int>:

string value = ((KeyValuePair<int, int>)comboBox1.SelectedValue).Value.ToString();

However, you should put a brakepoint there and check what type SelectedValue really is.

I assume it's KeyValuePair<int, int> because your source collection is Dictionary<int, int> and because of output string for SelectedValue.ToString() which is [1, 202].