如何解决＆＃39;值不能为空。参数名称：dataSet＆＃39;错误

Question

我在类中全局设置了数据集属性，如下所示，并在pageload event.so中绑定gridview，如下所示抛出错误 / 值不能为空。 参数名称：dataSet /

  

公共DataSet Ds
          {
              得到
              {
                  object temp = ViewState [＆＃34; Ds＆＃34;];
                  return temp == null？ null：temp as DataSet;
              }
              组               {
                  ViewState [＆＃34; Ds＆＃34;] =值;
              }
          }

    public void gridCustBind(int pageIndex)
    {
        try
        {
            //open the db connection if it is closed...  
            if (connection.State == ConnectionState.Closed)
                connection.Open();
            command = new SqlCommand();
            command.CommandText = "sp_Get_CustInfoSerach";
            command.CommandType = CommandType.StoredProcedure;
            command.Connection = connection;
            command.Parameters.AddWithValue("@PageIndex", pageIndex);
            command.Parameters.AddWithValue("@PageSize", int.Parse(ddlPaging.SelectedValue));
            command.Parameters.Add("@RecordCount", SqlDbType.Int, 4);
            command.Parameters["@RecordCount"].Direction = ParameterDirection.Output;

            //SqlParameter outParam = command.Parameters.Add("@bal", SqlDbType.Float);
            //outParam.Direction = ParameterDirection.Output;

            command.Parameters.Add("@bal", SqlDbType.Int, 4);
            command.Parameters["@bal"].Direction = ParameterDirection.Output;

            SqlDataAdapter daAcc = new SqlDataAdapter(command);

            daAcc.Fill(Ds);
           }
        catch (Exception ex)
        {
            lblMessageCustSerach.Text = ex.Message;
            lblMessageCustSerach.Visible = true;
        }  
                finally //Close db Connection if it is open....  
        {
            if (connection.State == ConnectionState.Open)
                connection.Close();

        }
    }        

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack == true)
        {

            gridCustBind(1);
            if (gridCustomer.Rows.Count > 0)
            {
                gridCustomer.DataSource = Ds;
                gridCustomer.DataBind();

            }

        }
    }