ASP.net C＃ConnectionString屬性尚未初始化

Question

我有一個具有編輯按鈕的gridview。當用戶點擊該按鈕時，gridview（顯示tbl_userContents表格）的內容會轉到某些文本框，然後他可以更改內容並單擊保存按鈕。當他單擊保存按鈕時，插入到tbl_contents表中的編輯內容和此內容的記錄將從tbl_userContents中刪除。

第一部分（插入到tbl_contents表）的作品...... 但第二部分（從tbl_userContents刪除）不工作，ex.Message顯示了這個錯誤：ConnectionString屬性尚未初始化

你能幫我解決這個問題嗎？！

這是我的代碼：

using System; 
    using System.Collections.Generic; 
    using System.Linq; 
    using System.Web; 
    using System.Web.UI; 
    using System.Web.UI.WebControls; 
    using System.Data.SqlClient; 
    using System.Configuration; 
    using System.IO; 

    public partial class manager_usercontents : System.Web.UI.Page 
    { 
    SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["PP"].ConnectionString); 
protected void Page_Load(object sender, EventArgs e) 
{ 

} 
protected void gvUserContents_SelectedIndexChanged(object sender, EventArgs e) 
{ 

} 
    protected void btnEditUserContent_Click(object sender, EventArgs e) 
{ 
    int id = Int32.Parse(((Button)sender).CommandArgument.ToString()); 
    Session.Add("ucid", id); 
    string sql = "select * from tbl_userContents where ucid=@id"; 
    try 
    { 
     SqlCommand cmd = new SqlCommand(sql, cn); 
     cmd.Parameters.AddWithValue("@id", id); 
     SqlDataReader dr; 
     cn.Open(); 
     dr = cmd.ExecuteReader(); 
     dr.Read(); 
     txtEditUserContentTopic.Text = dr["topic"].ToString(); 
     hfUserContentEdit.Value = dr["contentUrl"].ToString(); 
     txtEditUserContentNote.Text = dr["contentNote"].ToString(); 
     cmd.Dispose(); 
    } 
    finally 
    { 
     cn.Close(); 
     cn.Dispose(); 
    } 
} 
protected void btnsaveEditUserContent_Click(object sender, EventArgs e) 
{   
    //first we shoud save the user content in contents table... 
    string masir, strfilename, cont = string.Empty, sql; 
    try 
    { 
     if (fuEditUserFileUpload.HasFile) 
     { 
      masir = HttpContext.Current.Server.MapPath("../contents"); 
      strfilename = fuEditUserFileUpload.FileName; 
      fuEditUserFileUpload.SaveAs(masir + "\\" + strfilename); 
      cont = "contents\\" + strfilename; 
     } 
     else cont = hfUserContentEdit.Value; 


     sql = "insert into tbl_contents (topic,contentNote,contentUrl) values(@t,@contentN,@contentU)"; 
     SqlCommand cmd = new SqlCommand(sql, cn); 
     cmd.Parameters.Add("@t", txtEditUserContentTopic.Text); 
     cmd.Parameters.Add("@contentN", txtEditUserContentNote.Text); 
     cmd.Parameters.Add("@contentU", cont); 

     cn.Open(); 
     cmd.ExecuteNonQuery(); 
     cmd.Dispose(); 
    } 
    catch (Exception ex) 
    { 
     lblEditUserContentError.Style.Add("color", "red"); 
     lblEditUserContentError.Text = "the record does not successfully inserted" } 

    cn.Close(); 
    cn.Dispose(); 
    lblEditUserContentError.Style.Add("color", "green"); 
    lblEditUserContentError.Text = "the record successfully inserted"; 
    gvUserContents.DataBind(); 


    //then we should delete the user content record from the tbl_userContents table 
    int SessionID = Int32.Parse(Session["ucid"].ToString()); 
    sql = "delete from tbl_userContents where ucid=@id"; 
    try 
    { 
     SqlCommand cmd = new SqlCommand(sql, cn); 
     cmd.Parameters.AddWithValue("@id", SessionID); 
     cn.Open(); 
     cmd.ExecuteNonQuery(); 
    } 
    catch (Exception ex) 
    { 
     // lblDeleteError.Style.Add("color", "red"); 
     //lblDeleteError.Text = "the record does not deleted successfully."; 
     lblDeleteError.Text = ex.Message; 

    } 
    finally 
    { 
     // lblDeleteError.Style.Add("color", "green"); 
     // lblDeleteError.Text = "record deleted successfully"; 
     gvUserContents.DataBind(); 
     cn.Close(); 
    } 
} 

，這是我webConfig：

 <connectionStrings> 
<add name="PipelineProtection" connectionString="Data Source=MAHSA-PC;Initial Catalog=PipelineProtection;Integrated Security=True" /> 
<add name="PP" connectionString="Data Source=MAHSA-PC;Initial Catalog=PipelineProtection;Integrated Security=True" 
    providerName="System.Data.SqlClient" /> 

Answer 1

這裏發生了什麼事情在你的程序：

您最初定義CN爲SQL連接的對象。 cn已初始化。但是在你的按鈕事件（第一個函數）中，它完美地工作，然後在你的finally塊中，因爲cn.Close（），cn現在具有空值。所以它不適用於其他功能。

public partial class manager_usercontents : System.Web.UI.Page 
{ 
string connectStr=ConfigurationManager.ConnectionStrings["PP"].ConnectionString; 
SqlConnection cn; 

然後每次在點擊事件寫在開始下面一行：

cn =new SQLConnection(connectStr);