ASP.net C＃ConnectionString属性尚未初始化

Question

我有一个具有编辑按钮的gridview。当用户点击该按钮时，gridview（显示tbl_userContents表格）的内容会转到某些文本框，然后他可以更改内容并单击保存按钮。当他单击保存按钮时，插入到tbl_contents表中的编辑内容和此内容的记录将从tbl_userContents中删除。

第一部分（插入到tbl_contents表）的作品...... 但第二部分（从tbl_userContents删除）不工作，ex.Message显示了这个错误：ConnectionString属性尚未初始化

你能帮我解决这个问题吗？！

这是我的代码：

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(); 
    } 
} 

，这是我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

这里发生了什么事情在你的程序：

您最初定义CN为SQL连接的对象。 cn已初始化。但是在你的按钮事件（第一个函数）中，它完美地工作，然后在你的finally块中，因为cn.Close（），cn现在具有空值。所以它不适用于其他功能。

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

然后每次在点击事件写在开始下面一行：

cn =new SQLConnection(connectStr);