How to update the remaining days automatically from database to datagridview according to current date?

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I am making a windows application using C# .Net, I have DataGridView, a DateTimePicker and a textbox named as "days left" and a save button in that windows from. I have a database table named as "vehicle" and it includes two columns named as "expiry date" and "DaysLeft", I want to store data from windows form to the database table and it should store the DaysLeft either -ve or +ve value according to current date and I also want to update DaysLeft column automatically in DataGridView according to current date.

What I have tried:

I have tried the following code

private void dateTimePickerKhaas_ValueChanged(object sender, EventArgs e)
        {
            DateTime from = dateTimePickerKhaas.Value;
            DateTime to = DateTime.Now;
            TimeSpan Tspan = from - to;
            double days = Tspan.TotalDays;
            txtKDaysLeft.Text = days.ToString("0");
        }

private void btnKSave_Click(object sender, EventArgs e)
        {
                con.Open();
                String query = "INSERT INTO table_khaas ( ExpiryDate, DaysLeft) VALUES( '" + dateTimePickerKhaas.Value.ToString("MM/dd/yyyy") + "'  ,'" +txtKDaysLeft.Text + "')";
                SqlDataAdapter sda = new SqlDataAdapter(query, con);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                dataGridViewKhaas.DataSource = dt;
                
                con.Close();
                grd_fillKhaas();


                MessageBox.Show("Inserted Successfully");
                dateTimePickerKhaas.Value = DateTime.Now;
                txtKDaysLeft.Text = "";
                        
        }

public void grd_fillKhaas()
        {
            //con.Open();
            String query = "SELECT * FROM table_khaas";
            SqlDataAdapter sda = new SqlDataAdapter(query, con);
            DataTable dt = new DataTable();
            sda.Fill(dt);
            dataGridViewKhaas.DataSource = dt;
            //con.Close();
        }

Posted 12-Jun-17 9:49am

Member 13151446

Updated 12-Jun-17 11:35am

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Richard Deeming 12-Jun-17 16:29pm

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

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Richard Deeming · Accepted Answer · 2017-06-12T10:34:00

Remove the DaysLeft column, and calculate it when you query the table:

C#

public void grd_fillKhaas()
{
    using (var connection = new SqlConnection("..."))
    {
        var sda = new SqlDataAdapter("SELECT ExpiryDate, DateDiff(dd, GetDate(), ExpiryDate) As DaysLeft FROM table_khaas", connection);
        var dt = new DataTable();
        sda.Fill(dt);
        dataGridViewKhaas.DataSource = dt;
    }
}

C#

private void btnKSave_Click(object sender, EventArgs e)
{
    using (var connection = new SqlConnection("..."))
    using (var command = new SqlCommand("INSERT INTO table_khaas ( ExpiryDate ) VALUES ( @ExpiryDate )", connection))
    {
        command.Parameters.AddWithValue("@ExpiryDate", dateTimePickerKhaas.Value);
        
        connection.Open();
        command.ExecuteNonQuery();
    }
    
    grd_fillKhaas();
    

    MessageBox.Show("Inserted Successfully");
    dateTimePickerKhaas.Value = DateTime.Now;
    txtKDaysLeft.Text = "";
}

DATEDIFF (Transact-SQL) | Microsoft Docs[^]

Patrice T · Accepted Answer · 2017-06-12T11:35:00

Quote:
I have a database table named as "vehicle" and it includes two columns named as "expiry date" and "DaysLeft",

Advice: Never put volatile data in database, it is a design flow.
Volatile data is data that change very often, like every day. Because in order to use that column "DaysLeft", you always have to update it unless you know that update have already been done. Believe me, it is a major pain in real situation.

Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, anf this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]

How to update the remaining days automatically from database to datagridview according to current date?

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