problem with this code

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i have validate an item which does not allow duplicate value by using this code but i have problem on it

VB

If SQLstr <> Nothing Then
               MessageBox.Show("name is already used ")

           End If

this is my source code:

SQL

Try
           Dim curdate As String
           Dim recstatus As String



           curdate = Now.Date
           recstatus = "A"

           If txtuser.Text = "" Then
               MessageBox.Show("Blank Record is NOT accepted")
               Exit Sub
           End If

           If txtpass.Text = "" Then
               MessageBox.Show("Blank Record is NOT accepted")
               Exit Sub
           End If
           If txtcpass.Text = "" Then
               MessageBox.Show("Blank Record is NOT accepted")
               Exit Sub
           End If

           If txtpass.Text.Trim <> txtcpass.Text.Trim Then
               MessageBox.Show("Both Password and Confirm Password Not Match")
               Exit Sub
           End If

           If (Comlevel.SelectedIndex = -1) Or Comlevel.Text = "" Then
               MessageBox.Show("Please select Level")
               Exit Sub
           End If



           Mycn = New SqlConnection("Data Source=IMAN-PC;Initial Catalog=control car;Integrated Security=True")
           Mycn.Open()
           SQLstr = "insert into login values('" & recstatus & "','" & txtuser.Text & "','" & txtpass.Text & "','" & Comlevel.Text & "','" & usrID & "','" & curdate & "','" & usrID & "', '" & curdate & "')"
           command = New SqlCommand(SQLstr, Mycn)
           icount = command.ExecuteNonQuery

           If SQLstr <> Nothing Then
               MessageBox.Show("name is here")

           End If

           If icount = 1 Then
               MessageBox.Show("Record Added Successfully", "Add Record", MessageBoxButtons.OK, MessageBoxIcon.Information)
           Else
               MessageBox.Show("No Record Inserted", "Add Record", MessageBoxButtons.OK, MessageBoxIcon.Information)

           End If




           Mycn.Close()

       Catch ex As Exception


           MessageBox.Show(ex.Message & "Could Not Insert Record")
           'Mycn.Close()

Posted 4-May-12 1:52am

dr.dream

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codeBegin 4-May-12 7:59am

what is your problem

dr.dream 4-May-12 8:04am

i think it is on for loop statment
it show the message(name is already used) then
it show(record add successfuly)

3 solutions

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CPallini · Answer 1 · 2012-05-04T02:18:00

Solution 1

You may use the SQL clause EXIST to avoid inserting duplicate rows, see, for instance, the first question in the FAQ here[^].

Posted 4-May-12 2:18am

CPallini

Comments

Maciej Los 4-May-12 12:29pm

Nice link with examples. My 5

CPallini 4-May-12 16:11pm

Thank you.

**Manoj K Bhoir** · Answer 2 · 2012-05-04T02:53:00

You Have to Check that the User ID is Already Exist Or Not in DataBase.Refer the following Code :

VB

Dim _Result As Object
Dim _ObjCmd As System.Data.SqlClient.SqlCommand = New System.Data.SqlClient.SqlCommand
       _ObjCmd.CommandText = "Select * From Login Where UserID ='" & txtUser.Text & "'"
       _ObjCmd.Connection = _SQLConnection
       Try
           _SQLConnection.Open()
           _Result = _ObjCmd.ExecuteReader
           _SQLConnection.Close()
       Catch ex As Exception

       End Try
       If _Result Is DBNull.Value Then
           'Your Insert Code
       Else
           MessageBox.Show("User Id Already Exist.")
       End If

I hope it will help you.:)

Kschuler · Answer 3 · 2012-05-04T03:54:00

Your variable SQLstr is never going to equal nothing because you set the variable to your insert SQL three lines before that. So your if statement...

VB

If SQLstr <> Nothing Then
    MessageBox.Show("name is here")
End If

will ALWAYS be hit because SQLstr will ALWAYS have the text you set in it three lines before.

It's not the correct value to check to see if you already have a value in your database. I agree with Manoj K Bhoir and CPallini that you need to perform the check separately and by other means.

problem with this code

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