problem with ado.net application

M

mo/-/sin

hi. i m mohsin.....

i m making a ado.net application using c# and gui............ there
are four text boxes and 4 buttons in the windows application..........
the application is connected to servicemaintenance table which has 4
columns in sql server... thee 4 buttons in the application are button1
- add button2 - save button3 - delete and button4 - update... i hav
bind the application with the table.......... the coding for the whole
project is given below............ first three buttons are working
properly however when i click on update button it throws an error and
the error is NullRefrenceException was unhandled and below it is
written that
"Object reference not set to an instance of an object"...............
the line prefixed with '------' is giving error..............
plz provide me with the right code..............

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

namespace CITY_HOSPITAL
{

public partial class Form20 : Form
{
DataTable dt;
DataRow dr;
string code;
public Form20()
{
InitializeComponent();

}

private void textBox3_TextChanged(object sender, EventArgs e)
{

}

private void Form20_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the
'cITY_HOSPITALDataSet.SERVICESMAINTENANCE' table. You can move, or
remove it, as needed.

this.sERVICESMAINTENANCETableAdapter.Fill(this.cITY_HOSPITALDataSet.SERVICESMAINTENANCE);
textBox1.Enabled = false;
textBox2.Enabled = false;
textBox3.Enabled = false;
textBox4.Enabled = false;
button2.Enabled = false;
}

private void button1_Click(object sender, EventArgs e)
{
button2.Enabled = true;
textBox2.Enabled = true;
textBox3.Enabled = true;
textBox4.Enabled = true;
textBox2.Text = "";
textBox3.Text = "";
textBox4.Text = "";
int ctr, len;
string codeval;
dt = cITY_HOSPITALDataSet.Tables["SERVICESMAINTENANCE"];
len = dt.Rows.Count -1;
dr = dt.Rows[len];
code = dr["SERVICEID"].ToString();
codeval = code.Substring(5, 1);
ctr = Convert.ToInt32(codeval);
if ((ctr >= 1) && (ctr < 9))
{
ctr = ctr + 1;
textBox1.Text = "SER00" + ctr;
}
else if ((ctr >= 9) && (ctr < 99))
{
ctr = ctr + 1;
textBox1.Text = "SER0" + ctr;
}
else if (ctr >= 99)
{
ctr = ctr + 1;
textBox1.Text = "SER" + ctr;
}
button1.Enabled = false;
}

private void button2_Click(object sender, EventArgs e)
{
dt = cITY_HOSPITALDataSet.Tables["SERVICESMAINTENANCE"];
dr = dt.NewRow();
dr[0] = textBox1.Text;
dr[1] = textBox2.Text;
dr[2] = textBox3.Text;
dr[3] = textBox4.Text;
dt.Rows.Add(dr);

sERVICESMAINTENANCETableAdapter.Update(cITY_HOSPITALDataSet);
textBox1.Text = System.Convert.ToString(dr[0]);
textBox1.Enabled = false;
textBox2.Enabled = false;
textBox3.Enabled = false;
textBox4.Enabled = false;

this.sERVICESMAINTENANCETableAdapter.Fill(this.cITY_HOSPITALDataSet.SERVICESMAINTENANCE);
button1.Enabled = true;
button2.Enabled = false;
}

private void button3_Click(object sender, EventArgs e)
{
if (MessageBox.Show("ARE YOU SURE YOU WANT TO DELETE THIS
RECORD", "CONFIRMATION", MessageBoxButtons.YesNo,
MessageBoxIcon.Question) == DialogResult.Yes)
{
string code;
code = textBox1.Text;
if (textBox1.Text.Length == 0)
{
MessageBox.Show("PLEASE SELECT A VALID RECORD",
"ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error );
}
else
{
dr =
cITY_HOSPITALDataSet.Tables["SERVICESMAINTENANCE"].Rows.Find(code);
dr.Delete();

sERVICESMAINTENANCETableAdapter.Update(cITY_HOSPITALDataSet);
}
}


}

private void bindingNavigator1_RefreshItems(object sender,
EventArgs e)
{

}

private void groupBox1_Enter(object sender, EventArgs e)
{

}

private void button4_Click(object sender, EventArgs e)
{

}

private void dataGridView1_Click(object sender, EventArgs e)
{
textBox1.Enabled = true;
textBox2.Enabled = true;
textBox3.Enabled = true;
textBox4.Enabled = true;
button2.Enabled = true;

}

private void groupBox2_Enter(object sender, EventArgs e)
{

}

private void button4_Click_1(object sender, EventArgs e)
{
dt = cITY_HOSPITALDataSet.Tables["SERVICESMAINTENANCE"];
dr = dt.Rows.Find(code);
------ dr.BeginEdit();
dr[0] = textBox1.Text;
dr[1] = textBox2.Text.Trim();
dr[2] = textBox3.Text.Trim();
dr[3] = textBox4.Text.Trim();
dr.EndEdit();
}

}

}
 
I

Ignacio Machin ( .NET/ C# MVP )

hi. i m mohsin.....

i m making a ado.net application using c# and gui............ there
are four text boxes and 4 buttons in the windows application..........
the application is connected to servicemaintenance table which has 4
columns in sql server... thee 4 buttons in the application are button1
- add  button2 - save button3 - delete and button4 - update... i hav
bind the application with the table.......... the coding for the whole
project is given below............ first three buttons are working
properly however when i click on update button it throws an error and
the error is NullRefrenceException was unhandled and below it is
written that
"Object reference not set to an instance of an object"...............
the line prefixed with '------' is giving error..............
plz provide me with the right code..............
Click to expand...

Do not post the entire code, no body will run it and it will make
difficult to read.
Just post the line where the error occur.
In your case the error is simple, you are trying to use an object that
is not created.
For example if the line with error is:
dr[1] = textBox2.Text.Trim();

it could be cause textBox2 is null, or textBox.Text is null
 
M

mo/-/sin

hi. i m mohsin.....
Click to expand...
i m making a ado.net application using c# and gui............ there
are four text boxes and 4 buttons in the windows application..........
the application is connected to servicemaintenance table which has 4
columns in sql server... thee 4 buttons in the application are button1
- add  button2 - save button3 - delete and button4 - update... i hav
bind the application with the table.......... the coding for the whole
project is given below............ first three buttons are working
properly however when i click on update button it throws an error and
the error is NullRefrenceException was unhandled and below it is
written that
"Object reference not set to an instance of an object"...............
the line prefixed with '------' is giving error..............
plz provide me with the right code..............
Click to expand...

Do not post the entire code, no body will run it and it will make
difficult to read.
Just post the line where the error occur.
In your case the error is simple, you are trying to use an object that
is not created.
For example if the line with error is:
dr[1] = textBox2.Text.Trim();

it could be cause textBox2 is null, or textBox.Text is null
Click to expand...

there is nothing like that buddy........ all the text boxes contain
value..........
and the error is in the line dr.BeginEdit();
 
K

Ken Foskey

there is nothing like that buddy........ all the text boxes contain
value..........
Click to expand...

Not a good way to get help, seems a little insulting.
and the error is in the line dr.BeginEdit();
Click to expand...

I would look to your schema and ensure that you have loaded everything
you need in order to fulfil the relationships that you have built.
Though I would not expect this error on a beginedit.

Ken
 
M

mo/-/sin

Not a good way to get help, seems a little insulting.


I would look to your schema and ensure that you have loaded everything
you need in order to fulfil the relationships that you have built.  
Though I would not expect this error on a beginedit.

Ken
Click to expand...

i extremely apologise for that............
 

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