Write your code as below.
string checkl = "SELECT COUNT(*) as CountValue FROM Counter WHERE leftcount=1";
com = new SqlCommand(checkl, con);
com.CommandType = CommandType.Text;
da = new SqlDataAdapter(com);
DataTable dtcheckl = new DataTable();
da.Fill(dtcheckl);
int lcount = 0;
lcount =Convert.ToInt32(dtcheckl.Rows[0]["CountValue"].ToString());
This should work.