How to find duplicate records when insert into database in wpf using C#

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.NET3.5

Sir,
In my project I want to know how to avoid the duplicate records when insert
into database
One of my form, there is state code and state name text fields.
I want to insert the same state code only once.
How can I avoid the same state code when one try to insert it again

The code is as follows to insert:
Actually I didn't write the code to avoid the duplicate once,because I don't know the code exactly

C#

SqlCommand cmd = new SqlCommand();
                            
String str = "insert into State(Code,Name)values ('" + 
              this.txtstatecode.Text + "','" + this.txtstatename.Text + "')";
cmd.CommandText = str;
cmd.Connection = conn;
cmd.ExecuteNonQuery();                               

DataTable dt = new DataTable();

String str1 = "select code,name from state";
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = str1;

SqlDataAdapter adp = new SqlDataAdapter(cmd);
SqlCommandBuilder cb = new SqlCommandBuilder(adp);
                               
adp.Fill(dt);
                                
bs.DataSource = dt;
statedg5.ItemsSource = bs;

adp.Update(dt);
this.datagrid.Items.Refresh();

[Modified: added pre tags and modified spacing in code]

Posted 18-Jan-10 18:45pm

LukmanulHakeem.T

Updated 8-Apr-10 7:49am

William Winner

v2

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2 solutions

Solution 8

I would suggest you to use IF NOT EXISTS condition in your query to check for already existence of records.

IF NOT EXISTS (SELECT CODE FROM STATE WHERE CODE = ????)
BEGIN
    --INSERT RECORD HERE
END

This way you will have a single call to database table.

Posted 15-Apr-10 4:05am

Muhammad Umar Siddique

Updated 27-Apr-10 17:48pm

v3

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_Damian S_ · Accepted Answer · 2010-01-18T19:04:00

To check if a state and code exists, perform a select statement with a where clause specifying the state and code you are looking for.

If the select statement returns no records, it doesn't exist, so insert it into the database. If the select statement returns a record, do not insert it again as the state and code already exist.

example:

select code, name from state where code = '1234' and name = 'Smithville'

Another thing - you will need to remember to handle single quotes that exist in your state names when building your SQL string.