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Login Authentication from SQL Server database

I have login issue authentication on windows form C# application. Once I register user it send user data to a SQL Server database. When I am trying to log in. Even if credentials match to data in data base message box showing up. Please see the code below.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using travel_booking.UserControlers;
using System.Data.SqlClient;
namespace travel_booking
{
public partial class UserContrLogin : UserControl
{
internal Action<object, EventArgs> OnUserLogin;
UserContrRegister userContrRegister;
public UserContrLogin()
{
InitializeComponent();
}
public void setUserContrRegister(UserContrRegister userContrRegister)
{
this.userContrRegister = userContrRegister;
}
private void Exit_Click(object sender, EventArgs e)
{
Application.Exit();
}
private void LoginButton_Click(object sender, EventArgs e)
{
SqlConnection sqlConnection = new SqlConnection(#"//Removed by me as it is sensitive data");
sqlConnection.Open();
string query = "Select * from tblUser Where Email = ' " + txtEmail.Text.Trim() + "' and Password = '" + txtPassword.Text.Trim() + "'";
SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(query, sqlConnection);
DataTable dataTable = new DataTable();
sqlDataAdapter.Fill(dataTable);
if (dataTable.Rows.Count > 0)
this.Hide();
else
MessageBox.Show("Email or/and Password is/are invalid. Please try again");
sqlConnection.Close();
}
}
}

You can use this code to work much better
public void Login()
{
SqlConnection sqlConnection = new SqlConnection(#"//Removed by me as it is sensitive data");
sqlConnection.Open();
string query = "Select * from tblUser Where Email = #Email and Password = #Password";
SqlCommand command = new SqlCommand();
command.Connection = sqlConnection;
command.CommandType = CommandType.Text;
command.Text = query;
command.Parameters.AddWithValue("#Email", txtEmail.Text.Trim());
command.Parameters.AddWithValue("#Password", txtPassword.Text.Trim());
SqlDataReader reader = command.ExecuteReader();
if(reader.Read() == true)
{
this.Hide();
}
else
{
MessageBox.Show("Email or/and Password is/are invalid. Please try again");
}
}
I use the command.Parameters.AddWithValue() to avoid the concatenation of the string of your query that can cause an SQL INJECTION

How to get textbox data (txtusername.text) data from the windows form 1(frmlogin) to form 2(frmmain) SQL query

I facing error when want to pass my data which insert at Form1(frmLogin) to Form2(frmMain) SQL Query.
Form1(frmLogin)coding
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace SytelineAutoGenerateDocNum
{
public partial class frmLogin : Form
{
public frmLogin()
{
InitializeComponent();
}
private void btnLogin_Click(object sender, EventArgs e)
{
SqlConnection sqlcon = new SqlConnection(#"Data Source=P13L3CFN756\SQLEXPRESS;Initial Catalog=Syteline_Misc_DocNum;Persist Security Info=True;User ID=sa;Password=1234;");
string query = "SELECT *FROM [Syteline_Misc_DocNum].[dbo].[users] Where username = '" + txtUsername.Text.Trim() + "' and password = '" + txtPassword.Text.Trim() + "'";
SqlDataAdapter sda = new SqlDataAdapter(query, sqlcon);
DataTable dtbl = new DataTable();
sda.Fill(dtbl);
if (dtbl.Rows.Count == 1)
{
frmMain objFrmMain = new frmMain();
//objFrmMain.Value = txtUsername.Text;
//objFrmMain.ShowDialog();
objFrmMain.Show();
this.Hide();
}
else
{
MessageBox.Show("Check your username and password");
}
}
private void btnExit_Click(object sender, EventArgs e)
{
this.Close();
}
}
}
Form2(frmMain)Coding
private void buttonGDN_Click(object sender, EventArgs e)
{
con.Open();
SqlCommand cmd = new SqlCommand("Insert into DocNum (Date,UserID,BusinessUnit,RunningNumber,DocumentNumber)values('" + txtUsername.Text + "')");
}
My Error is (The Name "txtUsername" does not exist in the current context).
I have provided an image of the error I am getting Error screenshot
Any help is much appreciated, Thanks
What I have tried:
I have no idea on the Error.
I have tried to enable the System Configuration on the reference, this did not solve the issue.

Error when trying to update DataGridView using Microsoft Access

I am trying to show records in a DataGridView using Microsoft Access 2010. But the problem is each time i click on the button1 i get an error saying "The ConnectionString property has not been initialized"
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.OleDb;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Attendance_Generation_System
{
public partial class Take_attendance : Form
{
OleDbConnection conn = new OleDbConnection();
public Take_attendance()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
conn.ConnectionString=#"Provider = Microsoft.ACE.OLEDB.12.0; Data Source = F:\UNI WORK\7th Semester\Visual Programming\Database31.accdb; " + "User id = admin; " + "Password = "; ;
OleDbCommand cmd =new OleDbCommand("SELECT * FROM Attendancerecord");
OleDbDataAdapter add = new OleDbDataAdapter(cmd);
DataTable dt = new DataTable();
add.Fill(dt);
dataGridView1.DataSource=dt;
cmd.ExecuteNonQuery();
}
}
}

The error is clear that tells you the connection string is not assigned. So, you should assign the connection string for OleDbDataAdapter
var connectionString = #"Provider = Microsoft.ACE.OLEDB.12.0; Data Source = F:\UNI WORK\7th Semester\Visual Programming\Database31.accdb; " + "User id = admin; " + "Password = ";
using (var oledbCnn = new OleDbConnection(connectionString))
{
oledbCnn.Open();
var cmd = new OleDbCommand("SELECT * FROM Attendancerecord", oledbCnn);
OleDbDataAdapter add = new OleDbDataAdapter(cmd);
DataTable dt = new DataTable();
add.Fill(dt);
dataGridView1.DataSource = dt;
oledbCnn.Close();
}

Using if statement in c# for SQL

I'm trying to writing a basic c# program that read datas from SQL and writes results on 3 textboxes and a label. Here is my 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 PLAKA
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=TESTDB;Integrated Security=True");
SqlDataAdapter sda = new SqlDataAdapter("SELECT * FROM Project where ID = '" + textBox1.Text + "'", con);
DataTable dt = new DataTable();
sda.Fill(dt);
textBox1.Text = dt.Rows[0][0].ToString();
textBox2.Text = dt.Rows[0][1].ToString();
textBox3.Text = dt.Rows[0][2].ToString();
textBox4.Text = dt.Rows[0][3].ToString();
SqlDataAdapter oks = new SqlDataAdapter("SELECT * FROM Project where Status = 'YES'", con);
if (oks)
{
label1.Text = "POSITIVE";
}
else
{
label1.Text = "NEGATIVE";
}
}
}
}
I'm writing ID number and see the informations of this ID on text boxes in my first part of my code and this works perfectly
All i need that when value in the 'Status' raw is "YES", my program writes "POSITIVE", other else writes 'NEGATIVE' on label1
Meanwhile Status information writes on Textbox3.
For this code i got this error message: "Error 1 Cannot implicitly convert type 'System.Data.SqlClient.SqlDataAdapter' to 'bool'
How can i solve this problem?

Your If condition is wrong.
use this.
SqlDataAdapter oks = new SqlDataAdapter("SELECT * FROM Project where Status = 'YES'", con);
oks.fill(dataSet)
if (dataSet.Tables["Table"].Rows.Count > 1)
{
label1.Text = "POSITIVE";
}
else
{
label1.Text = "NEGATIVE";
}

custom query for datagridview

I am currently building an application in C#. In this application, people give values in a label and ​​that values will be saved in a database. This also works at the moment. What I want is the following:
The people can see their own values back in a datagridview. If I do this with the wizard of the datagridview I can't select label2.Text(this is the customerID).
The query I used below is the following:
SELECT * FROM prestaties WHERE gebruikerid = '" + label1.Text + "'";
But it doesn't work. I don't see anything in my datagrid.
Sorry for my bad English. I hope you can understand me.
The code below I already have, but it doesn't work
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
namespace Eindopdracht
{
public partial class resultaten : Form
{
public resultaten()
{
InitializeComponent();
dataGridView1.Show();
}
private string username;
public void displaydata(String ddata)
{
OleDbConnection conn = new OleDbConnection(#"provider= microsoft.jet.oledb.4.0;data source=C:\\Users\\Jeffrey\\Desktop\\Eindopdracht WOE\\Eindopdracht\\sample.mdb");
string select = "SELECT * FROM prestaties WHERE gebruikerid = '" + label2.Text + "'";
conn.Open();
OleDbDataAdapter dataAdapter = new OleDbDataAdapter(select, conn);
DataSet ds = new DataSet();
dataAdapter.Fill(ds);
dataGridView1.DataSource = ds.tables[0];
conn.Close();
}
public void setUsername(String name)
{
username = name;
label1.Text = username;
setID();
}
public void setID()
{
OleDbConnection vcon = new OleDbConnection(#"provider= microsoft.jet.oledb.4.0;data source=C:\\Users\\Jeffrey\\Desktop\\Eindopdracht WOE\\Eindopdracht\\sample.mdb");
string selectie = "SELECT id FROM inlog WHERE Username='" + label1.Text + "'";
OleDbCommand vcom1 = new OleDbCommand(selectie, vcon);
vcon.Open();
vcom1.ExecuteNonQuery();
OleDbDataReader dr = null;
dr = vcom1.ExecuteReader();
while (dr.Read())
{
var waarde = dr.GetValue(0);
label2.Text = waarde.ToString();
}

I don't know if my code is 100% correct. I've build this by myself. If I use the class displayData in the begin next to InitializeComponent(); I will get an error.