HOW TO GET THE SELECTED ITEM(S) IN A LIST VIEW CONTROL

HOW TO GET THE SELECTED ITEM(S) IN A LIST VIEW CONTROL ListView returns collections of selected items and indices through the SelectedItems and SelectedIndices properties. Note that these collections are empty, if no item is currently selected (lst.SelectedItems.Count == 0). The first item that is selected is lst.SelectedItems[0] The index of this item in the Items collection is lst.SelectedIndices[0]. So basically   lst.SelectedItems[0]   is the same as lst.Items[lst.SelectedIndices[0]]     You can also use check boxes. Set CheckBoxes to true for this. Through the CheckedItems and CheckedIndices properties you can see which items are checked.

KEYPRESS EVENT IN VB.NET

Handle Keyboard Input at the Form Level in VB.NET

Windows Forms processes keyboard input by raising keyboard events in response to Windows messages. Most Windows Forms programs process keyboard input by handling the keyboard events.

How do I detect keys pressed in VB.NET

You can detect most physical key presses by handling the KeyDown or KeyUp events. Key events occur in the following order:

  KeyDown
  KeyPress

  KeyUp

How to detect when the Enter Key Pressed in VB.NET

The following VB.NET code behind creates the KeyDown event handler. If the key that is pressed is the Enter key, a MessegeBox will displayed .

  If e.KeyCode = Keys.Enter Then
 MsgBox("enter key pressd ")

End If

How to get TextBox1_KeyDown event in your VB.Net source file ?

Select your VB.Net source code view in Visual Studio and select TextBox1 from the top-left Combobox and select KeyDown from top-right combobox , then you will get keydown event sub-routine in your source code editor.

  Private Sub TextBox1_KeyDown(...)..

End Sub

The following VB.NET source code shows how to capture Enter KeyDown event from a TextBox Control.

How to: Print a Form by Using the PrintForm Component (Visual Basic)

Visual Studio 2012

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The PrintForm component enables you to quickly print an image of a form exactly as it appears on screen without using a PrintDocument component. The following procedures show how to print a form to a printer, to a print preview window, and to an Encapsulated PostScript file.

To print a form to the default printer

1. In the Toolbox, click the Visual Basic PowerPacks tab and then drag the PrintForm component onto the form.
   The PrintForm component is added to the component tray.
   
2. In the Properties window, set the PrintAction property to PrintToPrinter.
   
3. Add the following code in the appropriate event handler (for example, in the Click event handler for a Print Button).
   
   PrintForm1.Print()
   

To display a form in a print preview window

1. In the Toolbox, click the Visual Basic PowerPacks tab and then drag the PrintForm component onto the form.
   The PrintForm component is added to the component tray.
   
2. In the Properties window, set the PrintAction property to PrintToPreview.
   
3. Add the following code in the appropriate event handler (for example, in the Click event handler for a Print Button).
   
   PrintForm1.Print()
   

To print a form to a file

1. In the Toolbox, click the Visual Basic PowerPacks tab and then drag the PrintForm component onto the form.
   The PrintForm component is added to the component tray.
   
2. In the Properties window, set the PrintAction property to PrintToFile.
   
3. Optionally, select the PrintFileName property and type the full path and file name for the destination file.
   If you skip this step, the user will be prompted for a file name at run time.
   
4. Add the following code in the appropriate event handler (for example, in the Click event handler for a Print Button).
   
   PrintForm1.Print() 

   Ref: http://msdn.microsoft.com/en-us/library/bb629268.aspx

KEYPRESS EVENT IN VB.NET

Handle Keyboard Input at the Form Level in VB.NET

Windows Forms processes keyboard input by raising keyboard events in response to Windows messages. Most Windows Forms programs process keyboard input by handling the keyboard events.

How do I detect keys pressed in VB.NET

You can detect most physical key presses by handling the KeyDown or KeyUp events. Key events occur in the following order:

  KeyDown
  KeyPress

  KeyUp

 

Note: Before a form can capture its key-related events, its keyPreview property MUST be set to TRUE

 

How to detect when the Enter Key Pressed in VB.NET

The following VB.NET code behind creates the KeyDown event handler. If the key that is pressed is the Enter key, a MessegeBox will displayed .

  If e.KeyCode = Keys.Enter Then
 MsgBox("enter key pressd ")

  End If

How to get TextBox1_KeyDown event in your VB.Net source file ?

Select your VB.Net source code view in Visual Studio and select TextBox1 from the top-left Combobox and select KeyDown from top-right combobox , then you will get keydown event sub-routine in your source code editor.

  Private Sub TextBox1_KeyDown(...)..

  End Sub

ADD, EDIT OR UPDATE A DATABASE

Before we start the coding for these new buttons, it's important to understand that the DataSet is disconnected from the database. What this means is that if you're adding a new record, you're not adding it to the database: you're adding it to the DataSet! Similarly, if you're updating or Deleting, you doing it to the DataSet, and NOT to the database. After you have made all of your changes, you THEN commit these changes to the database. You do this by issuing a separate command. But we'll see how it all works.
You'll need to add a few more buttons to your form - five of them. Change the Name properties of the new Buttons to the following:

btnAddNew
btnCommit
btnUpdate
btnDelete
btnClear

Change the Text properties of the buttons to Add New Record, Commit Changes, Update Record, Delete Record, and Clear/Cancel. Your form might look something like this:

We'll start with the Update Record button

Updating a Record

To reference a particular column (item) in a row of the DataSet, the code is this:

ds.Tables("AddressBook").Rows(2).Item(1)

That will return whatever is at Item 1 on Row 2.
As well as returning a value, you can also set a value. You do it like this:

ds.Tables("AddressBook").Rows(2).Item(1) = "Jane"

Now Item 1 Row 2 will contain the text "Jane". This won't, however, effect the database! The changes will just get made to the DataSet. To illustrate this, add the following code to your btnUpdate:

          ds.Tables("AddressBook").Rows(inc).Item(1) = txtFirstName.Text
          ds.Tables("AddressBook").Rows(inc).Item(2) = txtSurname.Text

          MsgBox("Data updated")

Run your programme, and click the Next Record button to move to the first record. "John" should be displayed in your first textbox, and "Smith" in the second textbox. Click inside the textboxes and change "John" to "Joan" and "Smith" to "Smithy". (Without the quotes). Now click your Update Record button.

Move to the next record by clicking your Next Record button, and then move back to the first record. You should see that the first record is now "Joan Smithy".
 
Close down your programme, then run it again. Click the Next Record button to move to the first record. It will still be "John Smith". The data you updated has been lost! So here, again, is why:

"Changes are made to the DataSet, and NOT to the Database"

To update the database, you need some extra code. Amend your code to this (the new lines are in bold, red text):

               Dim cb As New OleDb.OleDbCommandBuilder(da)

               ds.Tables("AddressBook").Rows(inc).Item(1) = txtFirstName.Text
               ds.Tables("AddressBook").Rows(inc).Item(2) = txtSurname.Text

               da.Update(ds, "AddressBook")

               MsgBox("Data updated")

The first new line is this:

Dim cb As New OleDb.OleDbCommandBuilder(da)

To update the database itself, you need something called a Command Builder. The Command Builder will build a SQL string for you. In between round brackets, you type the name of your Data Adapter, da in our case. The command builder is then stored in a variable, which we have called cb.
The second new line is where the action is:

da.Update(ds, "AddressBook")

The da variable is holding our Data Adapter. One of the methods of the Data Adapter is Update. In between the round brackets, you need the name of your DataSet (ds, for us). The "AddressBook" part is optional. It's what we've called our DataSet, and is here to avoid any confusion.


But the Data Adapter will then contact the database. Because we have a Command Builder, the Data Adapter can then update your database with the values from the DataSet.

Without the Command Builder, though, the Data Adapter can't do it's job. Try this. Comment out the Command Builder line (put a single quote before the "D" of Dim). Run your programme again, and then try and update a record. You'll get this error message:

The error is because you haven't got a command builder - a Valid Update Command.
Delete the comment from your Command Builder line and the error message goes away.
You should now be able to make changes to the database itself (as long as the Access database isn't Read Only).
Try it out. Run your programme, and change one of the records. Click the Update button. Then close the programme down, and load it up again. You should see your new changes displayed in the textboxes.



More tutorials like this at http://www.homeandlearn.co.uk

HOW TO CONNECT TO AN ACCESS (*.mdb OR *.accdb DATABASE IN VB.NET

Connecting to a database in .net could be a bit tricky to programmers of vb 6.0 and vb(a) who are already used to recordsets and the JET engine.

However, it is quite simple if you keep the following concepts in mind.

Data Connection
This provides a connection to your database. For the purpose of our example, we would use an oledb provider. Declare a variable as part of the oledb.oledbconnection method as follows:

Dim DBConn As New OleDb.OleDbConnection

Where DBConn is our connection variable.
We can now assign a connection string value to our connection object by:

                .ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & _
                                            My.Application.Info.DirectoryPath & _
                                           "\Database\test1.accdb;Persist Security  Info=False;"
                .Open()

Assuming our database is named test1.accdb and is located in a folder named database in the same folder as the application is located.


Command Object
This object is used to store SQL commands needed to specify requests to our database. It is declared as

Dim cmdSQL As New OleDb.OleDbCommand

where cmdSQL is any variable of your choice. The three main properties to specify in an Oledb Command object is its connection, command type and command text.

                                     cmdSQL.Connection = DBConn
                                     cmdSQL.CommandText = "SELECT * FROM YourTable"
                                     cmdSQL.CommandType = CommandType.Text

Data Adapter
This serves as a go-between to your dataset and connection string. it is declared similar to your connection object as

 Dim DatAdapter As New OleDb.OleDbDataAdapter(cmdSQL)

DataSet
This is similar to a recordset and is an in-memory representation of the requested table from the database.
it is declared as:

Dim DatSet As New DataSet 

The dataset is filled using the fill method of the data adapter by

DatAdapter .Fill(DatSet)

so that the whole code look like this:


    Public Sub OpenDbConn()

    Dim DBConn As New OleDb.OleDbConnection
    Dim cmdSQL As New OleDb.OleDbCommand
    Dim DatAdapter As New OleDb.OleDbDataAdapter(cmdSQL)
    Dim DatSet As New DataSet

        With DBConn
                .ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & _
                        My.Application.Info.DirectoryPath & "\Database\test1.accdb;Persist Security Info=False;"
                .Open()
        End With

        If DBConn.State = ConnectionState.Open Then

            With cmdSQL
                .Connection = DBConn
                .CommandText = "SELECT * FROM YourTable"
                .CommandType = CommandType.Text
            End With

            With DatAdapter
                .Fill(DatSet)
            End With

        End If
    End Sub