索引在下拉菜單中沒有變化C＃Asp.Net

Question

我有一個DropDownList從數據庫中填充。當我在索引1上選擇一條記錄時，它會得到正確的結果，但是當我選擇第二個索引時，它會出現相同的索引。它看起來像DropDownList默認顯示第一個索引。我如何在DropDownList中選擇變更索引？ 因此，如果將選擇索引3，結果必須來自索引3. 我試過DropDownList.SelectedItem，DropDownList.SelectedValue, DropDownList.SelectedIndex,DropDownList.Text但沒有效果似乎在那裏。在Page_Load中

public void load_Individual() 
    { 
     if (IsPostBack == false) 
     { 
      SqlDataAdapter sdaIndividual = new SqlDataAdapter("select * from tbl_trip", _connectionString); 
      DataTable dtIndividual = new DataTable(); 
      sdaIndividual.Fill(dtIndividual); 
      if (dtIndividual.Rows.Count > 0) 
      { 
       ddl_Individual.DataTextField = "TruckNo"; 
       ddl_Individual.DataValueField = "TruckNo"; 
       ddl_Individual.DataSource = dtIndividual; 
       ddl_Individual.DataBind(); 
      } 
     } 
    } 

的DropDownList

DropDownList的加載對於選擇價值觀

if (ddl_Individual.Text != string.Empty) 
     { 
      ddl_Individual.ClearSelection(); 
      adp = new SqlDataAdapter(@"Select * , '' as c1, '' as c2, 0 as c3 , 0 as c4 , 0 as c5 , 0 as c6, 0 as c7 , 0 as c8 from tbl_Trip 
      where TruckNo='" + ddl_Individual.SelectedValue + "'", _connectionString); 
      adp.Fill(Dt); 
      Session["mydata"] = Dt; 
      Response.Redirect("LoadReport.aspx"); 
     } 
     else 
     { 
      ScriptManager.RegisterClientScriptBlock(this, this.GetType(),"alertMessage","aler('select valid value')", true); 
     } 

Answer 1

ddl_Individual.ClearSelection(); 

此行是清除在下拉列表中選擇你有機會讀什麼之前用戶選擇的值。刪除它，因爲我認爲不需要它。

確保通過檢查回發到設置在頁面加載項：

if(!IsPostBack) 
{ 
    // Perform binding 
} 

如果下拉會觸發回發然後一定要設置AutoPostBack = true;

而且，考慮使用參數化查詢來幫助防止SQL注入攻擊。無論應用程序的規模如何，這都是一個很好的開發習慣。