ASP.net C# ConnectionString 属性尚未初始化

Question

我有一个带有编辑按钮的网格视图。当用户单击该按钮时，gridview 的内容（显示 tbl_userContents 表）进入一些文本框，然后他可以更改内容并单击保存按钮。当他点击保存按钮时，插入到 tbl_contents 表中的编辑内容和该内容的记录将从 tbl_userContents 中删除。

第一部分（插入到 tbl_contents 表）工作...... 但第二部分（从 tbl_userContents 中删除）不起作用，ex.Message 显示此错误：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();
    }
}

这是我的网络配置：

      <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

这是你的程序中发生的事情：

最初您将 cn 定义为 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）中它工作得很好，然后在你的 finally 块中，因为 cn.Close()，cn 现在有空值。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;

然后每次在您的点击事件中，在开头写下以下行：

   cn =new SQLConnection(connectStr);