Issue with scalar variable C# ASP.NET project

public void OnGet()
{

    String ID = Request.Query["UserID"];

    try
    {

        String connectionString = "Data Source=SQLTableSource";

        using (SqlConnection connection = new SqlConnection(connectionString))
        {

            connection.Open();

            String sql = "SELECT * FROM [JB_DB].[dbo].[Tble_SD_Users] WHERE UserID = @UserID;";

            using (SqlCommand commmand = new SqlCommand(sql, connection))
            {

                commmand.Parameters.AddWithValue("@UserID", ID);
                //commmand.Parameters.Add("@ID", System.Data.SqlDbType.Int).Value = Convert.ToInt32(id);
                //commmand.Parameters.AddWithValue("UserID", userInfo.UserID ?? (object)DBNull.Value);

                //commmand.Parameters.AddWithValue("@UserID", System.Data.SqlDbType.NVarChar).Value = userInfo.UserID;

                using (SqlDataReader reader = commmand.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        userInfo.ID = "" + reader.GetInt32(0);
                        userInfo.UserID = reader.GetString(1);
                        userInfo.firstName = reader.GetString(2);
                        userInfo.lastName = reader.GetString(3);
                        userInfo.userDepartment = reader.GetString(4);
                    }
                }

            }

        }

    }

public void OnGet()
{

    String ID = Request.Query["tStatus"];

    try
    {
        String connectionString = "Data Source=SQLTableSource";
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            //String sql = "SELECT TOP (1000) ISNULL([tNumber], ' ') [tNumber], ISNULL([tStatus], ' ') [tStatus], ISNULL([tApplication], ' ') [tApplication], ISNULL([tType], ' ') [tType], ISNULL([tDateLogged], ' ') [tDateLogged], ISNULL ([tDateUpdated], ' ') [tDateUpdated], ISNULL ([tDateClosed],' ') [tDateClosed], ISNULL([tDateLastChecked], ' ') [tDateLastChecked], ISNULL([tUserLogged], ' ') [tUserLogged], ISNULL([tCurrentlyWith], ' ') [tCurrentlyWith], ISNULL([tLoggedOrAdHocTTL], ' ') [tLoggedOrAdHocTTL] FROM [JB_DB].[dbo].[Tble_COF_IT_UK_Tickets];";
            String sql = "SELECT * FROM [JB_DB].[dbo].[Tble_COF_IT_UK_Tickets] WHERE tStatus = @tStatus;";
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.Parameters.AddWithValue("@tStatus", ID);
                //command.Parameters.Add("@ID", System.Data.SqlDbType.Int).Value = Convert.ToInt32(ID);
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        ticketInfo.ID = "" + reader.GetInt32(0);
                        ticketInfo.tNumber = reader.GetString(1);
                        ticketInfo.tStatus = reader.GetString(2);
                        ticketInfo.tApplication = reader.GetString(3);
                        ticketInfo.tType = reader.GetString(4);
                        ticketInfo.tDateLogged = reader.GetString(5);
                        ticketInfo.tDateUpdated = reader.GetString(6);
                        ticketInfo.tDateClosed = reader.GetString(7);
                        ticketInfo.tDateLastChecked = reader.GetString(8);
                        ticketInfo.tUserLogged = reader.GetString(9);
                        ticketInfo.tCurrentlyWith = reader.GetString(10);
                        ticketInfo.tLoggedOrAdHocTTL = reader.GetString(11);
                    }
                }
            }
        }
    }