That should work, if you are developing a WinForms project.
using System.data.SqlClient;
should then allow you to enter SqlCommand objects.
Try this:
If your code, find a random method and enter a new line.
On that line, type "SqlCommand" without the double quote characters.
When you type the "d" at the end, a small red outlined bar should appear under it.
Move the mouse over the bar. A small drop down should appear.
Open the drop down. Your should have two options: "using System.Data.SqlClient" and "System.Data.SqlClient.SqlCommand".
Select the "using" one - this should insert the appropriate
using
statement for you, and the SqlCommand should turn light blue.
If it doesn't happen like this, at which stage does it behave differently?