Problem in autonumber in C# winform by sqldatabase

Question

0.00/5 (No votes)

See more:

i try AutoNumber in TextBox From SqlDataBase,
but Problem Appear when AutoNumer Reach Number 10 after Number my AutoNumber Code show every Time Number 10

when i use Debug

C#

var cont = cd.ExecuteScalar();
Var cout show Value = 9

What I have tried:

My Code is:

C#

// AutoNumber
        private void Autonumber()
        {
            string Query = "select MAX(ReceiptNo) from Project1";
            SqlCommand cd = new SqlCommand(Query, con);
            try
            {
                con.Open();
                var cont = cd.ExecuteScalar();
                var count = (cont == DBNull.Value ? 1 : Convert.ToInt32(cont) + 1);
                txtRecpt.Text = count.ToString();
            }

            finally
            {
                con.Close();
            }
        }

Posted 6-Sep-20 22:46pm

Amar chand123

Updated 6-Sep-20 22:59pm

Maciej Los

v2

Add a Solution

Comments

F-ES Sitecore 7-Sep-20 5:34am

If your query is returning 9 then that is the biggest instance of ReceiptNo in the database so your problem lies elsewhere. If you think it should be more then check where\how you create new rows, but as already told in the solutions trying to do your own auto number is generally very bad practice.

Amar chand123 7-Sep-20 5:38am

Problem solved mistake in 'ReceiptNo' data type when i change column data type into 'INT' problem solved

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2020-09-06T22:59:00

Ignore the problem you have spotted - you have much worse.

What you are doing is a very bad idea: never "preallocate" numbers and assume they will work as an autonumber.

Think about it: SQL Server is a multiuser system: which means that multiple applications on multiple computers can access the same database at the same time.
Suppose you call Autonumber and get "123". I also call Autonumber from my computer and also get "123" because the database hasn't been changed yet.
One of use will INSERT a new record correctly, one of us won't. And if any other information references that autonumber (for example, InvoiceLines referencing an Invoice) then your info gets "mixed in" with mine because they are both using the same "autonumber".

Instead, use an IDENTITY column in your database and let SQL take care of it: you INSERT the row, it allocates the unique autonumber, and nothing ever gets messed up.

Don't try to do it yourself, it will end in tears.