I can't seem to insert data to my database - sql-server

Question

I am having issues with my code when I try to insert data into my database, the section where it checks for matching username keeps popping up the error to select another username. I don't know what I am doing wrong, any help will be appreciated.
This is my code:
'Connecting to SQL Database and executing Query
Dim Strconn As String = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\phermacy.mdf;Integrated Security=True;User Instance=True"
Dim Strcmd As String = "INSERT INTO tblstaff_info(id,fname,lname,sex,nationality,status,dob,age,nationality,state,address,phone,email,dateemp,username,password) VALUES ('" & txtregid.Text & "','" & txtfname.Text & "','" & txtlname.Text & "','" & cmbstaffsex.Text & "','" & cmbstatus.Text & "','" & dtpickerdob.Text & "','" & txtage.Text & "','" & txtnationality.Text & "','" & txtstateofo.Text & "','" & rtbaddress.Text & "','" & txtphone.Text & "','" & txtemail.Text & "','" & dtpdateemp.Text & "','" & txtusername.Text & "','" & txtpassword.Text & "');"
Dim da As New SqlDataAdapter
Dim ds As New DataSet
Dim sqlcmd As SqlCommand
sqlconn = New SqlConnection(Strconn)
Try
sqlconn.Open()
Catch ex As Exception
MsgBox("Could not connect to DataBase. Application will close now!", vbCritical, "Database Error")
End
End Try
sqlcmd = New SqlCommand(Strcmd, sqlconn)
da.SelectCommand = sqlcmd
sqlcmd.Dispose()
sqlconn.Close()
'Exception Handling-----------------------
Dim exc As Exception = Nothing
Try
da.Fill(ds)
Catch ex As Exception
exc = ex
Finally
If Not (exc) Is Nothing Then
MsgBox("User Name Already Exist. Please select a different User Name!", vbExclamation, "Already Exist")
txtusername.Focus()
Else
MsgBox("Save info Successful.", vbInformation, "Successful")
'Me.Close()
'loginform.Show()
End If
End Try

Answer 1

The whole User Instance and AttachDbFileName= approach is flawed - at best! When running your app in Visual Studio, it will be copying around the .mdf file (from your App_Data directory to the output directory - typically .\bin\debug - where you app runs) and most likely, your INSERT works just fine - but you're just looking at the wrong .mdf file in the end!
If you want to stick with this approach, then try putting a breakpoint on the connection's .Close() call - and then inspect the .mdf file with SQL Server Mgmt Studio Express - I'm almost certain your data is there.
The real solution in my opinion would be to
install SQL Server Express (and you've already done that anyway)
install SQL Server Management Studio Express
create your database in SSMS Express, give it a logical name (e.g. Pharmacy - check your spelling!)
connect to it using its logical database name (given when you create it on the server) - and don't mess around with physical database files and user instances. In that case, your connection string would be something like:
Data Source=.\\SQLEXPRESS;Database=Pharmacy;Integrated Security=True
and everything else is exactly the same as before...
Also see Aaron Bertrand's excellent blog post Bad habits to kick: using AttachDbFileName for more background info.