Abstract classes, MustInherit, MustOverride , Overrides VB NET

VB.NET > OOP > Abstract Class

Abstract classes specify members that must be implemented in the inheriting classes. Any class can inherit only from one abstract class. You we cannot create objects of an abstract class.

MustInherit

Specifies that a class can be used only as a base class and that you cannot create an object directly from it.

MustOverride  

Specifies that a property or procedure is not implemented in this class and must be overridden in a derived class before it can be used.

Overrides

Specifies that a property or procedure overrides an identically named property or procedure inherited from a base class.




Example:

Public Class Form1

  Public MustInherit Class Employee

    Private mFirstName As String
    Private mLastName As String

    Public Sub New(ByVal FirstName, ByVal LastName)
      mFirstName = FirstName
      mLastName = LastName
    End Sub

    Public Property FirstName() As String
      Get
        Return mFirstName
      End Get
      Set(ByVal value As String)
        mFirstName = value
      End Set
    End Property

    Public Property LastName() As String

      Get
        Return mLastName
      End Get
      Set(ByVal value As String)
        mLastName = value
      End Set
    End Property

    Public MustOverride Function Income() As Double
  End Class

  Public Class Teacher

    Inherits Employee

    Private mSalary As Double

    Public Sub New(ByVal FirstName, ByVal Lastname, ByVal salary)
      MyBase.New(FirstName, Lastname)
      mSalary = salary
    End Sub

    Public Property Salary() As String

      Get
        Return mSalary
      End Get
      Set(ByVal value As String)
        mSalary = value
      End Set
    End Property

    Public Overrides Function Income() As Double

      Return Salary() * 1.2
    End Function
  End Class

  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim mTeacher As New Teacher("John", "Smith", 100)
    Dim sal = mTeacher.Income ' 120
  End Sub

End Class

Export RadGridView to Bitmap full Size

Telerik > Windows Forms > Export RadGridView to Bitmap

Sometimes is useful to export Telerik Rad Grid to image to its full size without regard of scroll bars.




Example:

Private Function GetImage(grd As Telerik.WinControls.UI.RadGridView)

        grd.Visible = False
        grd.Dock = DockStyle.None
        Dim w = 0
        For Each col In grd.Columns
            w = w + col.Width
        Next
        grd.Width = w
        If grd.Rows.Count > 0 Then
            grd.Height = (grd.Rows.Count * grd.Rows(0).Height)
        Else
            grd.Height = 150
        End If

        Dim bitmap As New Bitmap(grd.Bounds.Width, grd.Bounds.Height)

        grd.DrawToBitmap(bitmap, grd.Bounds)
        grd.Dock = DockStyle.Fill
        grd.Visible = True

        Return bitmap
End Function

Alter SQL Server Examples

SQL Server > DDL > Alter

Alter Table

Modifies a table definition by altering, adding, or dropping columns and constraints.

Examples:

• Add new column to a table

    ALTER TABLE dbo.TABLE_NAME ADD FIELD_NAME nvarchar(MAX) NULL

• Add computed column

ALTER LOGIN

Changes the properties of a SQL Server login account. Examples:    1.Change user password       ALTER LOGIN sa WITH PASSWORD = 'your_password';    2.Enable user       ALTER LOGIN sa ENABLE;

CREATE TABLE SQL Server

SQL Server > SQL Statements > CREATE TABLE

CREATE TABLE statement creates a table in a database.

Syntax

CREATE TABLE table_name
(
   column_name data_type(size),
   ...
);

Example

CREATE TABLE [dbo].[Table1](

       [ID] [bigint] IDENTITY(1,1) NOT NULL,
       [Name] [nvarchar](50) NOT NULL,
       [Password] [nvarchar](50) NOT NULL,
 CONSTRAINT [PK_users1] PRIMARY KEY CLUSTERED
(
       [ID] ASC
)
) ON [PRIMARY]
GO

Putting Quotation Marks in a String C#

C# > String > Quote

const string quote = "\"";
string str = "Topic: " + quote + "Putting Quotation Marks in a String" + quote;

Disable Spin Editor GridViewDecimalColumn RadGridView

Telerik > Windows Forms > > RadGridView > Disable Spin Editor


GridSpinEditor represents a spin editor in RadGridView.

Example: How to disable GridSpinEditor in RadGridView

  Private Sub RadGrid_CellEditorInitialized(sender As Object, e As Telerik.WinControls.UI.GridViewCellEventArgs) Handles Me.CellEditorInitialized

        Dim spinEditor As GridSpinEditor = TryCast(Me.ActiveEditor, GridSpinEditor)
        If spinEditor IsNot Nothing Then
            Dim element As GridSpinEditorElement = spinEditor.EditorElement
            element.ShowUpDownButtons = False
            element.InterceptArrowKeys = False
            element.EnableMouseWheel = False
        End If
    End Sub

Arrow keys not trigger VB NET

VB.NET > Form > Methods > ProcessCmdKey

ProcessCmdKey method processes a command key.

Example:
Use ProcessCmdKey to catch arrow keys (arrow keys not trigger VB NET in form events)

Solution:

   

Protected Overrides Function ProcessCmdKey(ByRef msg As Message, ByVal keydata As Keys) As Boolean

        If keydata = Keys.Right Or keydata = Keys.Left Or keydata = Keys.Up Or keydata = Keys.Down Then
            OnKeyDown(New KeyEventArgs(keydata))
            ProcessCmdKey = True
        Else
            ProcessCmdKey = MyBase.ProcessCmdKey(msg, keydata)
        End If
    End Function

Private Sub RunForm_KeyDown(sender As System.Object, e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown

        If e.KeyCode = Keys.Right Then
        End If
End Sub