Asp.net 单击“提交”按钮时,对象引用未设置为对象的实例
我已经在asp.net中创建了一个网页 在右边,我有一个列表框,当页面加载时,它会绑定数据库中的数据,其Default.aspx代码如下所示Asp.net 单击“提交”按钮时,对象引用未设置为对象的实例,asp.net,Asp.net,我已经在asp.net中创建了一个网页 在右边,我有一个列表框,当页面加载时,它会绑定数据库中的数据,其Default.aspx代码如下所示 <asp:ListBox ID="ListOfSql" runat="server" SelectionMode="Single" DataTextField="sql_name" DataValueField="sql_text" style="margin-left: 0px; width:auto; h
<asp:ListBox ID="ListOfSql" runat="server"
SelectionMode="Single" DataTextField="sql_name" DataValueField="sql_text"
style="margin-left: 0px; width:auto; height:300px" EnableViewState="true">
</asp:ListBox>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.OracleClient;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Windows.Forms;
using System.IO;
using System.Threading;
public partial class _Default : System.Web.UI.Page
{
System.Data.OracleClient.OracleConnection conn = new OracleConnection("Data Source = orcl; user id=*****;password = *****; unicode = true;");
//OracleConnection conn = new OracleConnection("Data Source=orcl;Persist Security Info=True;User ID=system;password = ravi_123;Unicode=True");
DataTable dt = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
}
loadSqlList();
lblLastRefresh.Text = DateTime.Now.ToShortTimeString();
lblDate.Text = DateTime.Now.ToShortDateString();
Response.Cache.SetAllowResponseInBrowserHistory(false);
//============================================= Checking user logged in or not ===================================
//if (Session["txtUserName"] == null)
//{
// Response.Write("<Script Language ='JavaScript'> alert('Session Expired, please login again')</script>");
// conn.Close();
// Response.Redirect("login.aspx");
//}
//============================================= Checking user logged in or not (END) ===================================
//=====================User Ip Tracer =======================
string UserIp = Request.ServerVariables["http_x_forwarded_for"];
string UserHost = Request.ServerVariables["http_X_forwarded_for"];
string userMacAdd = Request.ServerVariables["http_x_forwarde_for"];
if (string.IsNullOrEmpty(UserIp))
{
UserIp = Request.ServerVariables["Remote_ADDR"];
UserHost = System.Net.Dns.GetHostName();
}
LblLoc.Text = UserIp;
LblHostName.Text = UserHost;
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();
Response.AddHeader("Pragma", "no-cache");
//=====================User Ip Tracer code end =======================
if (!IsPostBack)
{
}
}
protected void onclick_logout(object sender, EventArgs e)
{
conn.Close();
Session.Clear();
Response.Redirect("login.aspx");
}
protected void exportToExcel_Click(object sender, EventArgs e)
{
try
{
conn.Open();
string sql;
sql = txtQuery.Text.ToString();
OracleDataAdapter da = new OracleDataAdapter(sql, conn);
//================ User Details Data Insertion in DataBase Ends here ===============
da.Fill(dt);
ExportTableData(dt);
Response.Write("<Script>alert('Ip Locked in DB')</Script>");
}
catch (Exception ex)
{
lblError.Text = ex.Message.ToString();
}
}
protected void btnClear_clik(object sender, EventArgs e)
{
txtQuery.Text = string.Empty;
}
private void ExportTableData(DataTable dtdata)
{
string attach = "attachment;filename="+ListOfSql.SelectedItem.Text.ToString()+".xls";
Response.ClearContent();
Response.AddHeader("content-disposition", attach);
Response.ContentType = "application/ms-excel";
if (dtdata != null)
{
foreach (DataColumn dc in dtdata.Columns)
{
Response.Write(dc.ColumnName + "\t");
}
Response.Write(System.Environment.NewLine);
foreach (DataRow dr in dtdata.Rows)
{
for (int i = 0; i < dtdata.Columns.Count; i++)
{
Response.Write(dr[i].ToString() + "\t");
}
Response.Write("\n");
}
Response.End();
}
}
// References for this page
// http://forums.asp.net/t/1768549.aspx
protected void btnPreSqlExe_Click(object sender, EventArgs e)
{
txtQuery.Text = ListOfSql.SelectedItem.Text.ToString();
}
private void loadSqlList()
{
if (!IsPostBack)
{
conn.Open();
DataTable dt = new DataTable();
DataSet ds = new DataSet();
string preSql = "select sql_name, sql_text from cn_sql_log order by sql_name";
OracleDataAdapter da = new OracleDataAdapter(preSql, conn);
da.Fill(ds);
ListOfSql.DataSource = ds;
ListOfSql.DataTextField = "Sql_Name";
ListOfSql.DataValueField = "sql_Text";
ListOfSql.DataBind();
ListOfSql.SelectedIndex = 0;
conn.Close();
}
}
}
我正在调用加载页面上的loadSqlList(),以便从列表框中的数据库中获取列表。
现在我有一个提交按钮
<asp:Button ID="btnPreSqlExe" runat="server" Text="Sumbit"
onclick="btnPreSqlExe_Click">
</asp:Button>
现在,当我想在点击提交按钮,然后所选项目的文本应出现在文本框,在左侧
当我这样做时,我会得到一个错误页面
default.aspx.cs页面的完整代码如下所示
<asp:ListBox ID="ListOfSql" runat="server"
SelectionMode="Single" DataTextField="sql_name" DataValueField="sql_text"
style="margin-left: 0px; width:auto; height:300px" EnableViewState="true">
</asp:ListBox>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.OracleClient;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Windows.Forms;
using System.IO;
using System.Threading;
public partial class _Default : System.Web.UI.Page
{
System.Data.OracleClient.OracleConnection conn = new OracleConnection("Data Source = orcl; user id=*****;password = *****; unicode = true;");
//OracleConnection conn = new OracleConnection("Data Source=orcl;Persist Security Info=True;User ID=system;password = ravi_123;Unicode=True");
DataTable dt = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
}
loadSqlList();
lblLastRefresh.Text = DateTime.Now.ToShortTimeString();
lblDate.Text = DateTime.Now.ToShortDateString();
Response.Cache.SetAllowResponseInBrowserHistory(false);
//============================================= Checking user logged in or not ===================================
//if (Session["txtUserName"] == null)
//{
// Response.Write("<Script Language ='JavaScript'> alert('Session Expired, please login again')</script>");
// conn.Close();
// Response.Redirect("login.aspx");
//}
//============================================= Checking user logged in or not (END) ===================================
//=====================User Ip Tracer =======================
string UserIp = Request.ServerVariables["http_x_forwarded_for"];
string UserHost = Request.ServerVariables["http_X_forwarded_for"];
string userMacAdd = Request.ServerVariables["http_x_forwarde_for"];
if (string.IsNullOrEmpty(UserIp))
{
UserIp = Request.ServerVariables["Remote_ADDR"];
UserHost = System.Net.Dns.GetHostName();
}
LblLoc.Text = UserIp;
LblHostName.Text = UserHost;
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();
Response.AddHeader("Pragma", "no-cache");
//=====================User Ip Tracer code end =======================
if (!IsPostBack)
{
}
}
protected void onclick_logout(object sender, EventArgs e)
{
conn.Close();
Session.Clear();
Response.Redirect("login.aspx");
}
protected void exportToExcel_Click(object sender, EventArgs e)
{
try
{
conn.Open();
string sql;
sql = txtQuery.Text.ToString();
OracleDataAdapter da = new OracleDataAdapter(sql, conn);
//================ User Details Data Insertion in DataBase Ends here ===============
da.Fill(dt);
ExportTableData(dt);
Response.Write("<Script>alert('Ip Locked in DB')</Script>");
}
catch (Exception ex)
{
lblError.Text = ex.Message.ToString();
}
}
protected void btnClear_clik(object sender, EventArgs e)
{
txtQuery.Text = string.Empty;
}
private void ExportTableData(DataTable dtdata)
{
string attach = "attachment;filename="+ListOfSql.SelectedItem.Text.ToString()+".xls";
Response.ClearContent();
Response.AddHeader("content-disposition", attach);
Response.ContentType = "application/ms-excel";
if (dtdata != null)
{
foreach (DataColumn dc in dtdata.Columns)
{
Response.Write(dc.ColumnName + "\t");
}
Response.Write(System.Environment.NewLine);
foreach (DataRow dr in dtdata.Rows)
{
for (int i = 0; i < dtdata.Columns.Count; i++)
{
Response.Write(dr[i].ToString() + "\t");
}
Response.Write("\n");
}
Response.End();
}
}
// References for this page
// http://forums.asp.net/t/1768549.aspx
protected void btnPreSqlExe_Click(object sender, EventArgs e)
{
txtQuery.Text = ListOfSql.SelectedItem.Text.ToString();
}
private void loadSqlList()
{
if (!IsPostBack)
{
conn.Open();
DataTable dt = new DataTable();
DataSet ds = new DataSet();
string preSql = "select sql_name, sql_text from cn_sql_log order by sql_name";
OracleDataAdapter da = new OracleDataAdapter(preSql, conn);
da.Fill(ds);
ListOfSql.DataSource = ds;
ListOfSql.DataTextField = "Sql_Name";
ListOfSql.DataValueField = "sql_Text";
ListOfSql.DataBind();
ListOfSql.SelectedIndex = 0;
conn.Close();
}
}
}
使用系统;
使用System.Collections.Generic;
使用System.Linq;
使用System.Web;
使用System.Web.UI;
使用System.Web.UI.WebControl;
使用System.Data.OracleClient;
使用系统数据;
使用System.Data.SqlClient;
使用系统配置;
使用System.Windows.Forms;
使用System.IO;
使用系统线程;
公共部分类\u默认值:System.Web.UI.Page
{
System.Data.OracleClient.OracleConnection conn=新的OracleConnection(“数据源=orcl;用户id=****;密码=****;unicode=true;”;
//OracleConnection conn=neworacleconnection(“数据源=orcl;持久安全信息=True;用户ID=system;密码=ravi_123;Unicode=True”);
DataTable dt=新的DataTable();
受保护的无效页面加载(对象发送方、事件参数e)
{
如果(!IsPostBack)
{
}
loadSqlList();
lblLastRefresh.Text=DateTime.Now.ToShortTimeString();
lblDate.Text=DateTime.Now.ToShortDateString();
Response.Cache.SetAllowResponseInBrowserHistory(false);
//=========================================================================检查用户是否登录===================================
//if(会话[“txtUserName”]==null)
//{
//响应。写入(“警报(‘会话已过期,请重新登录’)”;
//康涅狄格州关闭();
//重定向(“login.aspx”);
//}
//=============================================================================================================================================================================================================================================
//===============================用户Ip跟踪器=======================
字符串UserIp=Request.ServerVariables[“http_x_forwarded_for”];
字符串UserHost=Request.ServerVariables[“http_X_forwarded_for”];
字符串userMacAdd=Request.ServerVariables[“http_x_forwarde_for”];
if(string.IsNullOrEmpty(UserIp))
{
UserIp=Request.ServerVariables[“Remote_ADDR”];
UserHost=System.Net.Dns.GetHostName();
}
LblLoc.Text=UserIp;
LblHostName.Text=UserHost;
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();
AddHeader(“Pragma”,“无缓存”);
//===============================用户Ip跟踪代码结束=======================
如果(!IsPostBack)
{
}
}
受保护的void onclick\u注销(对象发送方,事件参数e)
{
康涅狄格州关闭();
Session.Clear();
重定向(“login.aspx”);
}
受保护的void exportToExcel\u单击(对象发送方,事件参数e)
{
尝试
{
conn.Open();
字符串sql;
sql=txtQuery.Text.ToString();
OracleDataAdapter da=新的OracleDataAdapter(sql,conn);
//======================在数据库中插入的用户详细信息数据到此结束===============
da.填充(dt);
输出表数据(dt);
响应。写入(“警报('Ip锁定在DB')”;
}
捕获(例外情况除外)
{
lblError.Text=ex.Message.ToString();
}
}
受保护的void btnClear\u clik(对象发送方,事件参数e)
{
Text=string.Empty;
}
私有void ExportTableData(DataTable dtdata)
{
string attach=“attachment;filename=“+ListOfSql.SelectedItem.Text.ToString()+”.xls”;
Response.ClearContent();
AddHeader(“内容处置”,附件);
Response.ContentType=“应用程序/ms excel”;
如果(dtdata!=null)
{
foreach(dtdata.Columns中的数据列dc)
{
Response.Write(dc.ColumnName+“\t”);
}
Response.Write(系统、环境、换行符);
foreach(dtdata.Rows中的数据行dr)
{
对于(int i=0;i
如果未进行选择,则SQL.SelectedItem的列表将为空,因此调用.Text
将导致错误
尝试将代码更改为以下内容:
protected void btnPreSqlExe_Click(object sender, EventArgs e)
{
if(ListOfSql.SelectedItem != null)
{
txtQuery.Text = ListOfSql.SelectedItem.Text.ToString();
}
}
这样做,错误页面将被删除,但我不会将listbox的文本值获取到位于左侧的textbox。当选择某个项目时,您是否会收到该错误?当列表中的某个项目未被选中且按钮处于预设置状态时,我的解决方案将解决您的问题