Having problem connecting to database

Question

 Please i need help!!!

 

  What can i do?

 

my login form is giving error when i try to login after running the application. Below is the

error message:

 

 

 

My source 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 Sales_Invoice

{

public partial class frmLogin : Form

{

private object txtUserName;

private object txtPassword;

public frmLogin()

{

InitializeComponent();

}

private void label1_Click(object sender, EventArgs e)

{

}

private void btnExit_Click(object sender, EventArgs e)

{

this.Close();

}

private void btnLogin_Click(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(@"Data Source=ABJ-DEVSVR-01\MINTSQL;Initial Catalog=Contacts;Integrated Security=True");

SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) From Login where Username='" + txtUserName + "' and Password='" + txtPassword + "'", 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 frmLogin_Load(object sender, EventArgs e)

{

}

}

}