How to capture checkbox value in datalist and insert into data?

Hello, friends, I want to capture the checkbox value in datalist, and outside the datalist, there is a button for users to click, and it will save the checkbox value into database. I have a dropdownlist above the datalist for users to choose the staffName, when user select the staffName and check on some checkbox, click on button, the value of checkbox will save into the data.
dropdownlist name: ddlName
ddlName.DataTextField = StaffName
ddlName.DataValueField = StaffID
datalist : dlCapability
dlCapability.datakeyField = TechCodeID
checkbox: cbSelect
the insert statment is : INSERT INTO UsersTech (UserID, TechCodeID)
  VALUES (@UserID,@TechCodeID)
My code has a error : Conversion from string "TechCodeID" to type 'Integer' is not valid.
I cannot find the solution, can anyone help me ? Thank you!
These are my code :
  Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As ...