本文介绍了单击打印按钮时出错的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
您好。
我有一个Web表单，用户可以在表单上输入数据并将其保存到数据库中。用户还可以打印他们刚刚输入的数据的报告。好吧，当用户点击打印按钮时，它会调用另一个页面来显示报告。弹出该页面时会出现此错误：
Hello.
I have a web form that a user can input data on the form and save it to the database. The user can also print a report of the data that they just entered. Well, when the user clicks the print button it calls for another page to show the report. When that page pops up this error is in it:
Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
FinancialProfileFormA.Page_Load(Object sender, EventArgs e) in C:\Users\khopkins\Documents\Visual Studio 2010\Projects\SACSCOCLogin1.1\SACSCOCLogin1.1\FinancialProfileFormA.aspx.cs:45
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +91
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207
以下是打印按钮的代码：
Here is the code for the Print Button:
using System;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Text;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Configuration;
using System.Drawing.Printing;
using System.IO;
using System.Web.SessionState;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;
public partial class FinancialProfileFormA : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void ButtonPrint_Click(object sender, EventArgs e)
{
TextBoxINST_ID.Text = Session["inst_id"].ToString();
ClientScript.RegisterStartupScript(this.GetType(), "onclick", "<script language=javascript>window.open('ReportFormA.aspx','PrintMe','height=650px,width=800px,scrollbars=1');</script>");
}
以下是打印按钮调用页面的代码：
Here is the code for the page the print button calls:
using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using CrystalDecisions.Web;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.WebControls;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;
using CrystalDecisions.Windows.Forms;
using CrystalDecisions.ReportSource;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Xml.Linq;
using System.Web.SessionState;
namespace SACSCOCLogin1._1
{
public partial class ReportFormA : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
TextBoxINST_ID.Text = Session["inst_id"].ToString();
CrystalReportViewer1.Visible = true;
ReportDocument CrystalReport = new ReportDocument();
ParameterField paramField = new ParameterField();
ParameterFields paramFields = new ParameterFields();
ParameterDiscreteValue paramDiscreteValue = new ParameterDiscreteValue();
paramField.Name = "inst_id";
paramField.CurrentValues.Clear();
paramDiscreteValue = new ParameterDiscreteValue();
paramDiscreteValue.Value = TextBoxINST_ID.Text;
paramFields.Add(paramField);
CrystalReportViewer1.ParameterFieldInfo = paramFields;
CrystalReport.Load(Server.MapPath("~/Reports/FormAReport.rpt"));
string sessiontype = TextBoxINST_ID.Text;
CrystalReport.SetParameterValue("inst_id", TextBoxINST_ID.Text);
string sessionid = TextBoxINST_ID.Text;
CrystalReport.SetParameterValue("inst_id", TextBoxINST_ID.Text);
//CrystalReport.Refresh();
CrystalReport.SetDatabaseLogon("Adminr", "master22", @"SQL", "Hot");
CrystalReportViewer1.ReportSource = CrystalReport;
}
}
}
这是Print Helper页面的代码：
This is the code for the Print Helper page:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
using System.Text;
using System.Web.SessionState;
public class PrintHelper
{
public PrintHelper()
{
}
public static void PrintWebControl(Control ctrl)
{
PrintWebControl(ctrl, string.Empty);
}
public static void PrintWebControl(Control ctrl, string Script)
{
StringWriter stringWrite = new StringWriter();
System.Web.UI.HtmlTextWriter htmlWrite = new System.Web.UI.HtmlTextWriter(stringWrite);
if (ctrl is WebControl)
{
Unit w = new Unit(100, UnitType.Percentage); ((WebControl)ctrl).Width = w;
}
Page pg = new Page();
pg.EnableEventValidation = false;
if (Script != string.Empty)
{
pg.ClientScript.RegisterStartupScript(pg.GetType(), "PrintJavaScript", Script);
}
HtmlForm frm = new HtmlForm();
pg.Controls.Add(frm);
frm.Attributes.Add("runat", "server");
frm.Controls.Add(ctrl);
pg.DesignerInitialize();
pg.RenderControl(htmlWrite);
string strHTML = stringWrite.ToString();
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.Write(strHTML);
HttpContext.Current.Response.Write("<script>window.print();</script>");
HttpContext.Current.Response.End();
}
}
我该如何解决这个问题？我做错了什么？
How can I fix this? What did I do wrong?
推荐答案
这篇关于单击打印按钮时出错的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！