C# :: Read SQL Table To Datagrid

I have been struggling to implement a method for reading data from SQL server to my C# program. In the C# program I prepared a DataGrid (not a DataGridView) for the data to be shown in it using a button "Load Table". Now I just want to read a table which has 4 different columns which I also added to the DataGrid.

I have a DataAccessDB class and this is the code for establishing a connection:

const string DB_CONNECTION = @"It is known to me";
SqlConnection con;
SqlCommand cmd;
Controller myController;

Then, there is a code to reference controller:

public DataAccessDB(Controller refController) {
con = new SqlConnection(DB_CONNECTION);
cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.StoredProcedure;
myController = refController;
}

And this is the code for a List which I am going to use for filling the data to a DataGrid:

public List<ProductionStock> GetProductionStockFromDB() {
int productionStockId, amount;
decimal price;
string name, descript;

[code]....

And now the main part - how to read the data when I press a LoadTable button. The point here is that I already defined connection strings here as you can see, and in the method itself I guess I should not repeat it. The tutorials I have seen they do it everything in that one button.