Sending Messages

Getting Values

There are a number of constants that return values from the SendMessage function. You can also use the SendMessage function to get information from a control because, as it is a function it can return a value. These expose a number of useful properties which are not available with the standard VB control properties. These all begin with EM_ . A few are listed below

Const EM_CANUNDO = &HC6 ' Can we undo the last action?
Const EM_GETFIRSTVISIBLELINE = &HCE ' Get the first visible line in the rich text box
Const EM_GETLINE = &HC4 ' Get the current line number
Const EM_GETLINECOUNT = &HBA ' Get the total number of lines

To send a command to the text box to do any of these things and get a return value, use the following syntax:

Variable = SendMessage(TextBoxName.hWnd, Constant, 0, 0& )

Where Variable is a variable with the correct data type (in the case of using the above constants - Boolean), TextBoxName is the name of your text box, and Constant is one of the constants listed above. The other two properties are set to 0 and 0& (Null) as they are not needed.

The following example also uses a text box, but finds out if you can Undo in Text1, and if so enables the Undo menu item.

mnuUndo.Enabled = SendMessage(Text1.hWnd, EM_CANUNDO, 0, 0&) ' This will return either True or False

The following example uses a text box, finds out the number of lines, and displays it in a message box.

Dim nLines As Long
nLines = SendMessage(Text1.hWnd, EM_GETLINECOUNT, 0, 0&) ' This will return either True or False
Msgbox "This document has " & nLines & " lines"

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James Crowley

James Crowley United Kingdom

James first started this website when learning Visual Basic back in 1999 whilst studying his GCSEs. The site grew steadily over the years while being run as a hobby - to a regular monthly audien...

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