Problem in autonumber in textbox C#

Question

1.00/5 (1 vote)

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i Try AutoNumber for My Database in C#, But i Have A Problem in My AutoNumber Code,

Problem in AutoNumber

SrNo
00001
00002
00003
00004

if I Delete SrNo 00001 DataSet Then Next AutoNumber Show 00004 in TextBox but I Need Next Number Show in TextBox 00005

Can Any one Help Me and Fix My Problem

What I have tried:

My Code

private void Autonumber()
        {
            String connstring = ConfigurationManager.ConnectionStrings["Data"].ConnectionString;
            OleDbConnection con = new OleDbConnection(connstring);
            string Query = "select count(*) from customer";
            OleDbCommand cd = new OleDbCommand(Query, con);
            try
            {
                con.Open();
                int count = Convert.ToInt16(cd.ExecuteScalar()) + 1;
                txtNumber.Text = count.ToString("00000");
                txtNumber.Enabled = false;
                
            }
            
            finally
            {
                con.Close();
            }
        }

Posted 5-May-20 23:56pm

Amar chand123

Updated 6-May-20 2:08am

Garth J Lancaster

v2

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Comments

Amar chand123 6-May-20 6:10am

Now i try remove "Count" and use "max" in statement and is worked, us that right or not

Richard MacCutchan 6-May-20 6:34am

No, you should let the database generate sequence numbers automatically. I cannot recall the exact syntax but you need to declare one column of your customer table to be auto generated.

Maciej Los 6-May-20 8:09am

My virtual 5!

Richard MacCutchan 6-May-20 8:22am

Thanks, but it's only worth a 5 if I can remember the exact syntax.

Maciej Los 6-May-20 8:42am

Who cares about exact syntax? More important is to suggest an idea!

Richard MacCutchan 6-May-20 8:55am

If only people would take note of our suggestions.

Maciej Los 6-May-20 9:04am

;)

BillWoodruff 6-May-20 17:46pm

"Who cares about exact syntax? More important is to suggest an idea!" I care !

Maciej Los 7-May-20 0:41am

Ok, ok...
:D

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RickZeeland · Accepted Answer · 2020-05-06T01:29:00

Solution 1

You can use:

SELECT MAX(SrNo) FROM customer

See: SQL MIN() and MAX() Functions[^]

Posted 6-May-20 1:29am

RickZeeland

Comments

Maciej Los 6-May-20 8:09am

5ed!

Maciej Los · Accepted Answer · 2020-05-06T02:09:00

In single-user-environment custom autonumber function would be OK. But in multi-user-environment, it would fail.

You should implement what Richard MacCutchan mentioned in the comment to the question. See:
SQL SERVER 2012 – How to generate a varchar Sequence Number – Using Sequence Object | SQL Server Portal[^]

In case when database is placed is an Excel or Access file, you're in trouble. There's no such of functionality. You have to write custom function. See RickZeeland solution for details. Here is how to achieve that:
NextSrNo = MAX(SrNo) +1

Problem in autonumber in textbox C#

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