0

Okay,First of all let me introduce myself as newbee to this language.
this is my third day with program,I usually Practice at college where Visual studio 2010 is installed.
I have VS2012 ultimate.
If I sound silly forgive me,but I am really desperate here.

1st Problem,I couldnt create New SQL server database,so I added a newone with name database.mdf.
2nd I ceated a table and so on...now lets come to the code I have written.

Also I forgot to mention that same code works great with VS 2010 at my college PC.
Now I am confused.

error "Object reference not set to an instance of an object." at Form1_Load..I have mention in code too.

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.Configuration;
using System.Data.SqlClient;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        SqlConnection con;
        SqlCommand cmd;
        SqlDataAdapter sda;
        SqlDataReader sdr;
        DataSet ds;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            string st = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;//Object reference not set to an instance of an object.
            con = new SqlConnection(st);
            fill();

        }

        public void fill()
        {
            if (con.State != ConnectionState.Open)
            {
                con.Open();
            }

            string qry = "Select *from Table";
            cmd = new SqlCommand(qry, con);
            sda = new SqlDataAdapter(cmd);
            ds = new DataSet();
            sda.Fill(ds);
            ds.Tables[0].TableName = "abc";
            dataGridView1.DataSource = ds.Tables["abc"];
        }

        private void btn_Save_Click(object sender, EventArgs e)
        {
            string qry = "INSERT INTO Table(Name,Roll,Grade)Values('" + textBox1.Text + "', '" + textBox2.Text + "', '" + textBox3.Text + "')";
            cmd = new SqlCommand(qry, con);
            cmd.ExecuteNonQuery();
            fill();
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
        }

        private void btn_Delete_Click(object sender, EventArgs e)
        {

            string qry = "DELETE FROM Table WHERE Name='" + textBox1.Text + "'";
            cmd = new SqlCommand(qry, con);
            cmd.ExecuteNonQuery();
            fill();
            MessageBox.Show("File Deleted");
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
        }

        private void btn_update_Click(object sender, EventArgs e)
        {

            string qry = "Update Table set Name = '" + textBox1.Text + "',Grade = '" + textBox3.Text + "' where Roll = '" + textBox2.Text + "'";
            cmd = new SqlCommand(qry, con);
            cmd.ExecuteNonQuery();
            fill();
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }
    }
}

Edited by salesman91: adding

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Last Post by salesman91
0

one more thing ,I couldnt create dbo file(as I couldnt create New SQL database),so I created a new .mdf via add new connection.
Does this affect the coding?

0

Can you post your app.config file contents please. This hints that the connection string isn't in your config file.

0

here is the apps config.
I am really frustrated here please help:(

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="constr" connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\user\Documents\database.mdf;Integrated Security=True;Connect Timeout=30"></add> 
</connectionStrings>
</configuration>

Edited by salesman91: editing

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okay nevermind,I just deleted all my APs.config file from system and made a new one.Now it works.
Thank u all for ur support.
I am so glad to have this forum where I could ask all the stupid questions and no0one make fun of me.
cheers:P

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