我正在使用水晶报表打印学生的学费明细，但我遇到了例外. [英] I am using crystal reports for printing the fees details of students but i am getting exception.

问题描述

你好，

我正在使用水晶报表打印学生的学费明细，但我遇到了例外.
例外是"Object reference not set to an instance of an object."

我的代码是:

Hello there ,

I am using crystal reports for printing the fees details of students but i am getting exception.
Exception is "Object reference not set to an instance of an object."

My code is:

public Payreport(int studid) //studid is the student id which admin is selecting
        {
           
            this.studid = studid;
            
            ClsConnection.Conn.Open();
            string sql = "SELECT ADD_Master.FName, ADD_Master.MName, ADD_Master.LName, tbinst_details.inst_id, tbinst_details.inst_amt, tbinst_details.note,tbinst_details.inst_date, tbinst_details.inst_type FROM tbinst_details INNER JOIN ADD_Master ON ADD_Master.ADD_No = tbinst_details.stu_id where stu_id= '" + studid + "'";
            SqlDataAdapter dscmd = new SqlDataAdapter(sql, ClsConnection.Conn);
            DataSet ds = new DataSet();
            //DataSet ds = new DataSet();
            dscmd.Fill(ds);
           
            

            Pay objRpt = new Pay();
            objRpt.SetDataSource(ds.Tables[0]);
            crystalReportViewer1.ReportSource = objRpt;//getting exception here. 
            crystalReportViewer1.Refresh();
            ClsConnection.Conn.Close();

推荐答案

该错误的最可能原因是您没有为crystalReportViewer1分配任何内容:

The most likely reason for that error is that you haven''t assigned anything to crystalReportViewer1:

CrystalReportViewer crystalReportViewer1 = new CrystalReportViewer();

或相似.

在行上放置一个断点:

Or similar.

Put a breakpoint on the line:

crystalReportViewer1.ReportSource = objRpt;

，您将看到它包含null

尝试替换此代码

try to replace this code

crystalReportViewer1.ReportSource = ds.Tables[0];           
crystalReportViewer1.Refresh();
ClsConnection.Conn.Close();.            

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