Dynamically retrieve Oracle data from double parameter? - vb.net

Question

I have names and surnames to retrieve from DB, but It's not working as It should. I get names and surnames from a table where they are in separated columns. Names/surnames are displayed in combobox/textbox combination on my form. Now I need to retrieve this data, but there are only 4 fields in my DB to search, because all names/surnames are combined together in those fields (user request). My code works for 2 searches at a time, but not for all 4. Here is my code:
EDIT (this works now - I've separated parameters and added bracket in OR statements):
Using con As New OracleConnection("Data Source=myDB;User Id=Lucky;Password=MyPassword;")
con.Open()
Using cmd As New OracleCommand()
Dim SQL As String = "Select * FROM MyTable "
Dim conca As String = " Where "
Dim Person1 As String
Person1 = CmbName.Text.Trim & " " & TxtSurname.Text.Trim
If Not CmbName.Text = "" Then
SQL = String.Concat(SQL, conca, " (USER1 = :user OR USER2 = :user1)")
cmd.Parameters.Add(New OracleParameter("user", Person1))
cmd.Parameters.Add(New OracleParameter("user1", Person1))
conca = " and "
End If
Dim Person2 As String
Person2 = CmbName1.Text.Trim & " " & TxtSurname1.Text.Trim
If Not CmbName1.Text = "" Then
SQL = String.Concat(SQL, conca, " (ADMINISTRATOR1 = :admin OR ADMINISTRATOR2 = :admin1)")
cmd.Parameters.Add(New OracleParameter("admin", Person2))
cmd.Parameters.Add(New OracleParameter("admin1", Person2))
conca = " and "
End If
'Retrieve data using execute reader
cmd.Connection = con
cmd.CommandText = SQL
cmd.CommandType = CommandType.Text
Dim dr As OracleDataReader = cmd.ExecuteReader()
Dim dt As New DataTable
dt.Load(dr)
DataGridView1.DataSource = dt
End Using
I tried using brackets between "and" & "or", but this still doesn't work. Any suggestions ?

Answer 1

Although I don't like your approach, you should separate the queries or have one function retrieving results for you for each "Person" request. For your solution try to remove this: conca = " and " from the first and second 'if/else' statement. Add each result into your datatable and then load the gridview with the datatable.
You should call a function similar to this to get the results in a data reader and then feed your datatable. This way you can separate your queries. The tricky part is to have an elegant way to load your datagridview. My suggestion is to stop using datatables (they are very bad). You should use IEnumerable or List (Of Object) where you could add the results from each query.
Public Shared Function GetMeDatareader(yourQuery As String) As OracleDataReader
Using con As New OracleConnection("Data Source=myDB;User Id=Lucky;Password=MyPassword;")
con.Open()
Using cmd As New OracleCommand()
Dim SQL As String = yourQuery
'Retrieve data using execute reader
cmd.Connection = con
cmd.CommandText = SQL
cmd.CommandType = CommandType.Text
Dim dr As OracleDataReader = cmd.ExecuteReader()
Return dr
End Using
End Using
End Function