A first chance exception of type 'system.data.sqlclient.sqlexception' occurred in system.data.dll

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I am developing a desktop application in c# where i got this error while debugging my program .
I want to send the data from window application to the database of web application .And I connected the web application database.This is the second form it contain one more form e.i login form. So please kindly help me

What I have tried:

C#

public void timer1_Tick(object sender, EventArgs e)
{
    tik--;
    if (tik == 0)
    {
        timer1.Stop();
        string constring = @"Data Source=(LocalDB)\v11.0;Initial Catalog=D:\WEBSITE10\APP_DATA\INFO.MDF;Integrated Security=True";

        SqlConnection cnn = new SqlConnection(constring);
        try
        {
            string q = "update imagetable set Image_Capture = @pic where email = @Eml";
            SqlCommand scmd = new SqlCommand(q, cnn);
            scmd.Parameters.AddWithValue("@Eml", this.textBox2.Text);
            if (pictureBox1.Image != null)
            {
           MemoryStream     ms = new MemoryStream();
                pictureBox1.Image.Save(ms, ImageFormat.Jpeg);
                byte[] photo_array = new byte[ms.Length];
                ms.Position = 0;
                ms.Read(photo_array, 0, photo_array.Length);
                scmd.Parameters.AddWithValue("@pic", photo_array);

            }
            if (cnn.State != ConnectionState.Open)
                cnn.Open();
            SqlDataReader dr = scmd.ExecuteReader();
          //  cnn.Close();
            webcam.Stop();
        }
        catch (SqlException ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
}

Posted 20-Apr-16 8:05am

Member 12399485

Updated 21-Apr-16 4:04am

Tomas Takac

v4

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Comments

Kevin Marois 20-Apr-16 14:22pm

Your SQL statement(s) are probably incorrect. Paste them into SSMS and see what happens.

Member 12399485 20-Apr-16 14:35pm

this is working properly

Kevin Marois 20-Apr-16 14:47pm

You posted way too much code here, and it's not formatted. Can you post just the part that's failing?

Richard Deeming 20-Apr-16 15:09pm

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

EDIT: I see you've fixed that - well done! :)

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[^]

Sinisa Hajnal 21-Apr-16 2:35am

Too much code to read. Post the relevant code and format it. In general, check your connection string (make sure it connects), user rights and then check the queries you're sending to the database. Move them into stored procedures, execute them in query analyzer (not what you think you're sending, but take the string from the program).

Also, don't concatenate user input or you might find yourself without database to work with.

ZurdoDev 21-Apr-16 8:21am

The error will tell you exactly what the problem is. Please post the full error.

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OriginalGriff · Answer 1 · 2016-04-21T04:04:00

There are a number of things to note here: This is a timer Tick event handler, so the chances are that it occurs quite often, and quite frequently. And you don;t close or Dispose your SQL connections, which means they stay in existence until the Garbage collector comes along to remove them. Which may be next week, or next month, or ...
And Connections are scarce resources - you will run out of them a lot sooner than you will run out of memory and trigger the GC. Use a using block on your connection and command objects to ensure they are Disposed when they go out of scope.

And that leads to the second problem: as a result of the first problem you have an active SqlDataReader open when you exit - so you may well get problems from that when you try to do the next update. Use a using block on the reader as well.

And the third is: why the heck are you using a DateReader to do an update? Use ExecuteNonQuery instead.

But the main thing is: why are you doing this in a timer anyway? Particularly when you try to update and read images, this can take considerable time, and you will be monopolising your database to a stupid degree if the tick period is at all frequent.
Only ever update your DB if something has changed, not in a timer!