Shows the data from the database into the gridview using csharp

Question

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SQL

SELECT S.Marks,S.QPName,B.Class,B.BthNo,B.Batchdate,B.Attender 
FROM STUDDET S,Batch B where S.BthId = B.BthId and  S.StudId = '55334'

when i execute the above query output as follows;

Marks   QpName         Class     Bthno     Batchdate     Attender

56	REO_2011	REO	B120RE	2011-09-26 	NIRANJAN
64	REO_2011	REO	B120RE	2011-09-26 	NIRANJAN

in run mode as follows;

Student id    txt_studid(textbox)  Show (Button)

when i enter the student id and click the show button, the record show be displayed into the gridview

Show Button code as follows;

C#

 private string SQl;
    private SqlDataReader Dr;
    private SqlDataCon SCon = new SqlDataCon();



SQl = "SELECT S.Marks, S.QPName,B.Class,B.BthNo,B.Batchdate,B.Attender FROM STUDDET S,Batch B";
 SQl = SQl + "where S.BthId = B.BthId and  s.StudId = '" + txt_Studid.Text.ToString() + "'";
        try
        {
            Dr = SCon.ReadSql(SQl);
            this.GridView1.DataSource = Dr;
            this.GridView1.DataBind();
            Dr.Close();
        }
        catch (Exception e1)
        {
            Label4.Text = e1.Message.ToString();
            return;
        }

when i enter the student id in the textbox and click the Show button error shows as follows;

object reference not set to an instance of object.

please help me.

what is the problem in my Show Button code.

Rgds,
Narasiman P.

Posted 1-May-13 1:15am

Member 8054539

Updated 1-May-13 1:22am

Tejas Vaishnav

v2

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Comments

ZurdoDev 1-May-13 8:00am

The first problem is you are open to SQL injections, meaning I could do anything I want to your database. You need to use parameters in your queries. Second, what line of code is causing the error?

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Member 10012743 · Answer 1 · 2013-05-01T02:14:00

Mr. Narasiman,
Please check the following code, It may help :

using System.Data.SqlClient;
using System.Data;

private string SQl;

DataSet ds = new DataSet();
DataTable dt = new DataTable();

SqlConnection con = new SqlConnection( /* connection string (database) */);
SqlDataAdapter adapter = new SqlDataAdapter();

SQl = "SELECT S.Marks, S.QPName,B.Class,B.BthNo,B.Batchdate,B.Attender FROM STUDDET S,Batch B";
SQl = SQl + "where S.BthId = B.BthId and s.StudId = '" + txt_Studid.Text.ToString() + "'";

SqlCommand command = new SqlCommand(SQ1,con);
try
{
adapter.SelectCommand = command;
adapter.Fill(ds, "OUTPUT");
dt=ds.Tables{"OUTPUT"];
adapter.Dispose();
command.Dispose();
this.GridView1.DataSource = dt;
this.GridView1.DataBind();

}
catch (Exception e1)
{
Label4.Text = e1.Message.ToString();
return;
}

try it and reply