i want to update data in gridview,but facing exception .

Question

1.00/5 (3 votes)

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VS2013

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace School
{
public partial class Classes : Form
{

SqlCommandBuilder scb;
SqlDataAdapter adapter;
DataSet dataset;

public Classes()
{
InitializeComponent();
}

private void Classes_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'schoolDataSet.Add_Student' table. You can move, or remove it, as needed.
this.add_StudentTableAdapter.Fill(this.schoolDataSet.Add_Student);

}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string strconnection = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\Abbii\Documents\School.mdf;Integrated Security=True;Connect Timeout=30";
SqlConnection connection = new SqlConnection(strconnection);

SqlCommand cmd = new SqlCommand();
cmd.CommandText = "select Id,F_NIC,Name,Class FROM Add_Student WHERE Class='"+comboBox1.SelectedItem +"'";
cmd.Connection = connection;
DataSet dataset=new DataSet();
SqlDataAdapter adapter = new SqlDataAdapter(cmd);

adapter.Fill(dataset);
dataGridView1.DataSource = dataset.Tables[0];

}

private void button1_Click_1(object sender, EventArgs e)
{
scb = new SqlCommandBuilder(adapter);//nullreference exception was unhandeld.
adapter.Update(dataset);

}

}

}

Posted 12-Jun-15 8:44am

Member 11762109

Updated 12-Jun-15 9:16am

Sergey Alexandrovich Kryukov

v2

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Comments

virusstorm 12-Jun-15 14:54pm

What is your exception?

Member 11762109 12-Jun-15 16:17pm

An unhandled exception of type 'System.NullReferenceException' occurred in School.exe

Additional information: Object reference not set to an instance of an object

virusstorm 12-Jun-15 16:19pm

Which statement? We are willing to help, but you got to be able to describe the problem in detail.

Member 11762109 12-Jun-15 16:21pm

i'm really sorry sir,i'm beginner.error is showing on this line
scb = new SqlCommandBuilder(adapter);
as i have mentioned by comment in my code.

virusstorm 12-Jun-15 16:31pm

Understood.

So your issue is actually self explanatory. Your "adapter" object that you are passing into SqlCommandBuilder is null. You never actually instantiated or set it to value.

Looking your code, there is a sequence that needs to take place. You need to for "adapter" to have a value. The value in "comboBox1" needs to change in order for the correct event to fire to set the value. I see bigger problems with your code, however. What is the goal you are trying to achieve? I might be able to put together a better prototype for you that could put you a better path.

gggustafson 12-Jun-15 17:35pm

You need to respond to virusstorm. He is trying to help you.

Member 11762109 14-Jun-15 16:46pm

Thankyou so much for your support sir :)

[no name] 12-Jun-15 14:58pm

This is what is called a code dump. It is not a question or a description of a problem. We are not your debugging service. Debug your code, find the exception, research what it means and fix it.

Sergey Alexandrovich Kryukov 12-Jun-15 15:16pm

With System.Windows.Forms, better use System.Windows.Forms.DataGridView.
—SA

ZurdoDev 12-Jun-15 15:26pm

What's the error?

Member 11762109 12-Jun-15 16:17pm

An unhandled exception of type 'System.NullReferenceException' occurred in School.exe

Additional information: Object reference not set to an instance of an object

ZurdoDev 12-Jun-15 16:21pm

Look, if you want help you have to post enough information. What in the world are we supposed to do with that error? The error means something was null. How would we know what's null. We can't see your computer. We can't run your code.

So, look at the line of code the error refers to and fix the problem.

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shashank7977 · Accepted Answer · 2015-06-12T22:36:00

As per my Knowledge, change the comboBox1_SelectedIndexChanged function as you are using local variables with same name as the global variable. Please change the code as per below implemented function. It will work.

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string strconnection = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\Abbii\Documents\School.mdf;Integrated Security=True;Connect Timeout=30";
SqlConnection connection = new SqlConnection(strconnection);

SqlCommand cmd = new SqlCommand();
cmd.CommandText = "select Id,F_NIC,Name,Class FROM Add_Student WHERE Class='"+comboBox1.SelectedItem +"'";
cmd.Connection = connection;
dataset=new DataSet();
adapter = new SqlDataAdapter(cmd);

adapter.Fill(dataset);
dataGridView1.DataSource = dataset.Tables[0];

}

private void button1_Click_1(object sender, EventArgs e)
{
scb = new SqlCommandBuilder(adapter);//nullreference exception was unhandeld.
adapter.Update(dataset);

}