data not inserting in tables.

hello sir / madam,

i am new to c#.net and i like to program,i have a table named login which have id,username and password columns, i also have a login form to send data in Login table i want to store input data in table but i am receiving the error - " An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll". what am i doing wrong? i am using visual studio 2015.please help! thank you.here is my code -

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 login

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void btnLogin_Click(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Log.mdf;Integrated Security=True;Connect Timeout=30;");

SqlDataAdapter sda = new SqlDataAdapter("Select Count (*) From Login where username ='" + userNametextBox.Text + "'and password='" + PasswordtextBox.Text + "'", con);

DataTable dt = new DataTable();

sda.Fill(dt);

if (dt.Rows[0][0].ToString() == "1")

{

this.Hide();

Main ss = new Main();

ss.Show();

}

else

{

MessageBox.Show("Please check your username and password ");

}

private void btnInsert_Click(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Log.mdf;Integrated Security=True;Connect Timeout=30;");

SqlDataAdapter sda = new SqlDataAdapter("Select Count (*) From Login where username ='" + userNametextBox.Text + "'and password='" + PasswordtextBox.Text + "'", con);

SqlCommandBuilder cmb = new SqlCommandBuilder(sda);

//DataTable dt = new DataTable();

DataSet ds = new DataSet();

sda.Fill(ds, "Login");

ds.Tables[0].Constraints.Add("Id", ds.Tables[0].Columns[0], true);

DataRow row;

row = ds.Tables[0].NewRow();

row["username"] = userNametextBox.Text;

row["password"] = PasswordtextBox.Text;

ds.Tables[0].Rows.Add(row);

sda.Update(ds.Tables[0]);

MessageBox.Show("record added", this.Text);

}

private void userNametextBox_TextChanged(object sender, EventArgs e)

{

}

Too much to tell and not enough space to type the whole response here.

1/ Try to avoid DataAdaptor, DataTable and DataSet objects wherever possible. In my (strictly personal) opinion they are the overkill for the kind job typically we want to perform.

2/ NEVER EVER write you data access code in events like Button Click or anywhere in front-end related code, for example, form.

3/ Create separate classes for EVERYTHING. Because eventually you are going to need it anyway. For example, there should be class for User (typically called as a model), class with methods (these methods user data access layer) to save, delete and retrieve users (typically called as a business access layer) and a data access layer to do actually do the job.

You may wish to visit this link for details : http://www.webcodeexpert.com/2014/01/how-to-create-3-tier-application-in.html

Whatever you are attempting to do is simple, but I think you start learning how to do it in proper way. Because once you get used to this, you will have difficult time changing later.

Sorry, I didn't answer your question!

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Nitin Sontakke10y ago
Accepted answer
Too much to tell and not enough space to type the whole response here.
1/ Try to avoid DataAdaptor, DataTable and DataSet objects wherever possible. In my (strictly personal) opinion they are the overkill for the kind job typically we want to perform.
2/ NEVER EVER write you data access code in events like Button Click or anywhere in front-end related code, for example, form.
3/ Create separate classes for EVERYTHING. Because eventually you are going to need it anyway. For example, there should be class for User (typically called as a model), class with methods (these methods user data access layer) to save, delete and retrieve users (typically called as a business access layer) and a data access layer to do actually do the job.
You may wish to visit this link for details : http://www.webcodeexpert.com/2014/01/how-to-create-3-tier-application-in.html

Whatever you are attempting to do is simple, but I think you start learning how to do it in proper way. Because once you get used to this, you will have difficult time changing later.
Sorry, I didn't answer your question!