Use inheritance on forms for simpler and more robust source code

By using inheritance, source code can be made simpler and more robust.

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By using inheritance, source code can be made simpler and more robust. In this case, I'm dealing with stored procedures to write the contents of various forms to SQL Server. By using inherited forms from a form called BaseTable, in which all actions are predefined, I only have to worry about the parameters of the command object.

Code:

Public Class BaseTable
    Inherits System.Windows.Forms.Form
'
'Just the piece of code for saving an item is given
'
    Protected Overridable Sub AddPutParameters(ByVal Cmd As SqlClient.SqlCommand)
    End Sub


    Public Sub SaveItem()

        Dim Success As Boolean = True

        Try
            Dim Cmd As New SqlClient.SqlCommand()
            Cmd.Connection = New SqlClient.SqlConnection(_connectionString)
            Cmd.Connection.Open()
            Cmd.CommandType = CommandType.StoredProcedure
            Cmd.Parameters.Add(New SqlClient.SqlParameter("@id", SqlDbType.UniqueIdentifier))
            Cmd.Parameters("@id").Direction = ParameterDirection.Output
            AddPutParameters(Cmd)
            Cmd.ExecuteNonQuery()
        Catch ex As Exception
            Success = False
        End Try

        If Success Then
            HandleSuccess
        End If

    End Sub

End Class

To save a record in the derived forms you just have to implement the parameters that are specific to the table the form handles.

Public Class frm_COUNTRY

    Inherits BaseTable

    Protected Overrides Sub AddPutParameters(ByVal Cmd As SqlClient.SqlCommand)
        Cmd.Parameters.Add("@name", _name.Text)
        Cmd.Parameters.Add("@code", _code.Text)
        Cmd.CommandText="_spPUT_COUNTRY"

    End Sub

This was first published in May 2003

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