從表中選擇計數

Question

我的應用程序需要幫助，因為我試圖在每次搜索后顯示產品總數！ 我做了一個選擇語句，每次我使用單選按鈕列表和一個搜索框搜索產品時，它都會從我的表 Product 中顯示一行。 搜索可以是用戶名或產品 ID，然后用戶可以選擇該行並將其從 gridview 中刪除。 我還貼了一個標簽，應該顯示剩余的產品數量。 這個標簽應該給我網格視圖中的產品數量！ 我的問題是我使用的標簽只顯示第一，只生成記錄，我需要顯示產品總數。

代碼：

   using System;
   using System.Collections.Generic;
   using System.Linq;
   using System.Web;
   using System.Web.UI;
   using System.Web.UI.WebControls;

    public partial class Admin_AdminUserControl_Product : System.Web.UI.UserControl 
    {
       DataBaseConn Db = new DataBaseConn();

      Basket _b = new Product(); 
    protected void Page_Load(object sender, EventArgs e)
   {


         // Label shows only one record at a time
         lblQueue.Text = _b.Queue().ToString();


    }



  protected void btnSearch_Click(object sender, EventArgs e)
   {
     grid.DataSource = _b.SelectRow(rdoField.SelectedValue,txtSearch.Text);
     grid.DataBind();
      lblMsg.Text = "";
      btnRemove.Enabled = false;
      grid.SelectedIndex = -1;
  }
  protected void btnRemove_Click(object sender, EventArgs e)
  {
      if (_b.RemoveProduct(grid.SelectedRow.Cells[1].Text))

        lblMsg.Text = "Product is removed";
      else
          lblMsg.Text = "Unable to remove a Product!";
     grid.DataBind();
     btnRemove.Enabled = false;
  }
    protected void grid_SelectedIndexChanged(object sender, EventArgs e)
  {

      btnRemove.Enabled = true;
 }

類產品

  public DataTable Data(string txtField, string Value)
  {

    string SQL = String.Format("Select * from Product where {0} like'%{1}%'", txtField, Value);
    return Data(SQL);

}
public DataTable Data(string Query)
{
    try
    {
        return Db.RunQuery(Query);
    }
    catch
    {
        return new DataTable();
    }

 }

 public bool RemoveProduct(string ProductId)
{

    this.ProductID = ProductId;
    return Delete();
}

public DataTable SelectRow(string Field, string Value)
 {

    string sql = string.Format("SELECT TOP 1 * FROM Product where {0} like '%{1}%' ORDER BY 
       ProductID ASC", Field, Value);
    return SelectRow(sql);

 }

 public DataTable SelectRow(string Query)
 {
    try
    {
        return Db.RunQuery(Query);
    }
    catch
    {
        return new DataTable();
    }

 }
   //This label should show number of all products i.e from 0- any number
     public int Queue()
   {
    int customers;
    String sql = String.Format("Select Count(*) from Product");
    customers = Db.RunQuery(sql).Rows.Count;
    return customers;


   }

 }

Answer 1

我從你對 DataTables 的使用中猜測 Db.RunQuery 正在返回一個 DataTable？ 如果是這樣的話

.Rows.Count

將只是您的查詢返回的行數。 在這種情況下只有一個..所以如果返回的確實是一個 DataTable 你會像這樣訪問數據

customers = Convert.ToInt32(dt.Rows[0][0])

但這也只是假設 RunQuery 正在執行基本填充，返回數據表，而不是對數據表執行其他操作。

針對查詢http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar%28v=vs.110%29.aspx 使用ExecuteScalar 也可能更簡單

//I'm guessing this is something you'd add to your Db class. The ability to ExecuteScalar
    cmd.CommandText = "Select Count(*) from Product";
     customers = (Int32) cmd.ExecuteScalar();

Answer 2

使用以下代碼：

protected void datalistcatagory()
    {

        //SqlDataAdapter da = new SqlDataAdapter("Select Catagory_ID,Catagory_Name from tbl_catagory where Catagory_ID=Catagory_ID", con);

        using (SqlCommand cmd = new SqlCommand("Select (c.Catagory_ID), COUNT(c.Catagory_ID) As CID, c.Catagory_Name from tbl_NewPost sc join tbl_catagory c on c.Catagory_ID=sc.Catagory_ID Group by c.Catagory_Name, c.Catagory_ID Order by CID DESC"))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    if (dt.Rows.Count > 0)
                    {


                        Label4.Text = dt.Rows.Count.ToString();

                    }
                    Repeater1.DataSource = dt;
                    Repeater1.DataBind();
                }
            }
        }