Question

我想创建动态<asp:table ID=""...>，我希望通过从我的datareader读取第一个单元格并将其整合到一个totalAmount列，此列必须显示累计数字....

try
{
    sqlconnection();
    sqlcommand("", sqlconnection);
    sqlconnection.open();
    sqldatereader dr;
    dr = sqlcommand.executereader();
    if (dr.HasRows)
    {
        //create column names;
        table_ShowReport.Rows.Add(new TableRow());
        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell());
        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2;
        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = "Amount";

        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell());
        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2;
        table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = "Total";


        //here I wantend to get the initial value to my total:
        double total = double.parse(dr["amount"].tostring());

        while (dr.Read())
        {
            table_ShowReport.Rows.Add(new TableRow());
            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell());
            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2;
            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = dr["amount"].tostring();

            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell());
            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2;
            table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = total.tostring();


            total += double.parse(dr["amount"].tostring());
        }
    }
    sqlconnection.close();
}
catch (exception ex)
{
    respose.write(ex.message);
}

但它向我显示了这个错误：

无数据时无效尝试读取在场。

请帮帮我。感谢

丹娘

Answer 1

您必须在尝试从SqlDataReader读取之前调用dr.Read() 。

我建议在读取行之前将total变量初始化为零。然后在调用total之后但在显示总金额之前，将dr.Read()设置为更新后的金额。像这样：

double runningTotal = 0d; while (dr.Read()) { table_ShowReport.Rows.Add(new TableRow()); table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell()); table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2; table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = dr["amount"].ToString(); table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Add(new TableCell()); table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].BorderWidth = 2; runningTotal += double.Parse(dr["amount"].ToString()); table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells[table_ShowReport.Rows[table_ShowReport.Rows.Count - 1].Cells.Count - 1].Text = runningTotal.ToString(); } } sqlconnection.Close();

以下是重构的完整代码，所以更清楚：

private static void PopulateReport(Table table, string connection) { table.Rows.Clear(); PopulateReportRow(table, "Amount", "Total"); string commandText = @"..."; using (SqlConnection conn = new SqlConnection(connection)) { conn.Open(); using (SqlCommand comm = new SqlCommand(commandText, conn)) { using (SqlDataReader reader = comm.ExecuteReader()) { double total = 0d; while (reader.Read()) { double amount = (double)reader["amount"]; total += amount; PopulateReportRow(table, amount.ToString("N"), total.ToString("N")); } } } } } private static void PopulateReportRow(Table table, string amountValue, string totalValue) { const int cellBorderWidth = 2; int rowIndex = table.Rows.Add(new TableRow()); TableCell amountCell = new TableCell(); table.Rows[rowIndex].Cells.Add(amountCell); amountCell.BorderWidth = cellBorderWidth; amountCell.Text = amountValue; TableCell totalCell = new TableCell(); table.Rows[rowIndex].Cells.Add(totalCell); totalCell.BorderWidth = cellBorderWidth; totalCell.Text = totalValue; }

Answer 2

在你到达第一行之前，你试图从读者那里阅读。

您应该将其设置为0并在您正在进行的循环中填充它。

Answer 3

protected void Btnlogin_Click（object sender，EventArgs e）

{

    SqlConnection con=newSqlConnection("connection string"); 
    SqlCommand cmd = new SqlCommand();
    cmd.CommandText = "select * from tbluser where username='" + txtusername + "' and passworde='" + txtpassworde + "'";
    cmd.Connection = con;
    if (con.State == ConnectionState.Closed) con.Open();
    SqlDataReader dr = cmd.ExecuteReader();
    while (dr.Read())
    {
       if (dr["username"] == txtusername.Text.Trim() && dr["passworde"] == txtpassworde)
        {
            Response.Redirect("kala.aspx");
            return;
        }

   }
}

代码正确但未进入下一页

没有数据时无效尝试读取

3 个答案: