What this code mean ???

[Roomi7]

Private Sub txtName_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtFirstName.Validating, txtLastName.Validating
If CType(sender, TextBox).Text = "" Then
MessageBox.Show("You must enter a first and last name.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
e.Cancel = True
End If
End Sub


I write this code from the book and it's work but I don't know what I wrote??
What is ...

1 - CType mean?
2 - Sender mean?
3 - TextBox mean? (My TextBox name is txtFirstName why I use TextBox not txtFirstName?)


Thanks all,

[PT Exorcist]

CType() converts the first argument to the type of data specified by the second argument

[MrPolite]

Originally posted by Roomi7
Private Sub txtName_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtFirstName.Validating, txtLastName.Validating
If CType(sender, TextBox).Text = "" Then
MessageBox.Show("You must enter a first and last name.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
e.Cancel = True
End If
End Sub


I write this code from the book and it's work but I don't know what I wrote??
What is ...

1 - CType mean?
2 - Sender mean?
3 - TextBox mean? (My TextBox name is txtFirstName why I use TextBox not txtFirstName?)


Thanks all,

question 1 was answered
3 was answered too: The second argument of ctype gets the type of the object, which is TextBox. That's why you use that
2 -> sender is the object that has fired this event. So if txtFirstName fired a Validating event the sender object would be txtFirstName. If txtLastName fired the event, then sender would be txtLastName.

[Pirate]

Originally posted by Roomi7
Private Sub txtName_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtFirstName.Validating, txtLastName.Validating
If CType(sender, TextBox).Text = "" Then
MessageBox.Show("You must enter a first and last name.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
e.Cancel = True
End If
End Sub

I write this code from the book and it's work but I don't know what I wrote??
What is ...

1 - CType mean?
2 - Sender mean?
3 - TextBox mean? (My TextBox name is txtFirstName why I use TextBox not txtFirstName?)
Thanks all,

the object that raises the event is the sender .In your case , I think it's textbox object .

your now converting the expression into TextBox data type object "text".

this example explain it more :

Dim dic As Decimal = 1.002
Dim byt As Byte
byt = CType(dic, Byte)
MsgBox(byt.ToString)

[Pirate]

too late......

[Roomi7]

Thanks alot now it's clear to me