C# Visual Studio2019 中的 System.InvalidCastException

Question

I was trying to get IDs of combobox items in order to store them in the code and use them to replace labels whenever combobox selected items are changed. However, i encountered this error. I used the first var testID to get the IDs of cbx items. then inserted it into my getbyid method and converted it into INT. IT is actually an object. So when I debugged it, it crashed. So is there any way to solve this problem?

var testID = cbxTakeTest.SelectedValue;
var Test = new TestManager().GetById(Convert.ToInt32(testID));

               lblTakeTestQuestion1.Text = Test.Q1;
               lblTakeTestQuestion2.Text = Test.Q2;
               lblTakeTestQuestion3.Text = Test.Q3;

Value member was chosen as ID in the table where test names are stored

Answer 1

Your question was already answered here: Get ID of item selected in ComboBox

In short just apply ToString() to your testID.