Troubles passing args by ref

[Mike Hildner]

I've downloaded this code that's in VB.NET - it allows any object to be placed in a status bar panel - button, progress bar etc. I *think* I've converted it to C# ok (it compiles anyway). But now, trying to call a method, I'm running into something I don't know how to fix.

Here's the code I'm calling:

		public StatusBarChild(ref object obj, ref StatusBar sb, ref Int16 intPanelNumber, Int32 intMargin) 
		{ 
			ChildObject = (Control)obj; 
			StatusBar = sb; 
			Panel = intPanelNumber; 
			Margin = intMargin; 
			ChildObject.Parent = StatusBar; 
			Resize(); 
			ChildObject.Visible = true; 
		}

Calling with:

sbcProgressBar = new fr.free.marcon.e.StatusBarChild(progressBar1, statusBar1, 1, 2);

The compiler is complaining about the three args that get passed by ref, for example, "cannot convert from 'System.Windows.Forms.StatusBar to 'ref object''" for the first arg.

I tried just adding a ref in front of progressBar1, but then another error - "cannot convert from ref ...StatusBar to ref object".

Can anyone help me out? I might have converted the VB code incorrectly, but not really sure.

TIA,
Mike

[Danial]

sbcProgressBar = new fr.free.marcon.e.StatusBarChild(progressBar1, statusBar1, 1, 2);


Your fuction is expecting object as a parameter where as you are passing progress bar.

try

int i=1;

sbcProgressBar = new fr.free.marcon.e.StatusBarChild(ref (object)progressBar1, ref statusBar1, ref i, 2);

[hellswraith]

also, objects are passed by ref automatically. You don't need to put the ref keyword in for them.

Also, that code is not optimal.

Instead of this argument:
ref object obj

You should change it to
ref Control obj

Then you can get rid of the cast in the first line of the code. What this will do is force you to pass in a control to this method, and if you don't, the compiler will complain before hand. You really can't just pass any ol object into this method, it has to be of a control type.

[Mike Hildner]

Thanks both for the assistance. I need a little more I'm no expert at C#, as you can probably tell, just trying to understand what's going on here.

I did what hellswraith suggested and changed from object to Control, that at least made sense to me.

public StatusBarChild(ref Control ctrl, ref StatusBar sb, ref Int16 intPanelNumber, Int32 intMargin) 
		{ 
			ChildObject = ctrl; 
			StatusBar = sb; 
			Panel = intPanelNumber; 
			Margin = intMargin; 
			ChildObject.Parent = StatusBar; 
			Resize(); 
			ChildObject.Visible = true; 
		}

Now, trying to call this with

fr.free.marcon.e.StatusBarChild sbcProgressBar = new fr.free.marcon.e.StatusBarChild(progressBar1, statusBar1, 1, 2);

and I get "Argument '1': cannot convert from 'System.Windows.Forms.ProgressBar' to 'ref System.Windows.Forms.Control'
"

So I try to cast the ProgressBar into a Control

fr.free.marcon.e.StatusBarChild sbcProgressBar = new fr.free.marcon.e.StatusBarChild((Control)progressBar1, statusBar1, 1, 2);

and I get "Argument '1': cannot convert from 'System.Windows.Forms.Control' to 'ref System.Windows.Forms.Control'"

Allright. Object are passed by ref automatically? I don't understand my error then. Even if I try to force ref like this

fr.free.marcon.e.StatusBarChild sbcProgressBar = new fr.free.marcon.e.StatusBarChild(ref (Control)progressBar1, statusBar1, 1, 2);

Then my error is "A ref or out argument must be an lvalue" - which I think I understand and makes sense, but I just don't get the proper way to call the constuctor.

I realize this is quite familiar to my first post, but I just wanted to be clear with the steps taken so far.

Thanks,
Mike

[Mike Hildner]

I think I get it now. If I remove the ref in the constructor, there's no need to pass by ref, and there's no need to cast the progress bar into a control - which didn't make sense anyway. That seems to work, anyway.

[hellswraith]

You all squared away now?

[Mike Hildner]

Originally posted by hellswraith
You all squared away now?

I believe so, and thanks for asking.

My whole deal here was because I was bent on putting a progress bar inside of status bar panel. Trying to get that rich GUI.

Searched this forum and found some link to code that did that written in VB.NET. Manually converted to C#, and I think that's where my original problem came from.

FWIW, here's the code.

// Put ProgressBar in panel [1]
fr.free.marcon.e.StatusBarChild sbcProgressBar = new fr.free.marcon.e.StatusBarChild(progressBar1, statusBar1, 1, 2);
.
.
.
using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;

// Converted the VB author's code to C# 20040902
// If this works, it was converted by Mike Hildner,
// if it doesn't, I don't know who did it.

/*
' StatusBarChild class
'
' To put any object (a progressbar, a button...) in a statusbar panel in a VB.Net project
' E. Marcon, aug. 2004
' http://e.marcon.free.fr
*/

namespace fr.free.marcon.e
{
	class StatusBarChild
	{		
		Control ChildObject;         // The progressbar or any child control
		StatusBar StatusBar;        // The statusbar
		Int16 Panel;                // The status panel
		Int32 Margin;               // The margin between the panel's edge and the progressbar


	// API SendMaessageA in User32: returns the rectangle (RECT structure) used to display a status-bar panel
	[DllImport("user32.dll")]
	public static extern long SendMessageA(Int32 hwnd, Int32 msg, Int32 wParam, ref RECT lParam);
	public const long WM_USER = 0x400;
	//public const long WM_USER = &H400;
	public const long SB_GETRECT = WM_USER + 10;
	// RECT structure to get the panel's display rectangle
	public struct RECT
	{
		public Int32 Left;
		public Int32 Top;
		public Int32 Right;
		public Int32 Bottom;
	}

		//public StatusBarChild(ref Control ctrl, ref StatusBar sb, ref Int16 intPanelNumber, Int32 intMargin)
		public StatusBarChild(Control ctrl, StatusBar sb, Int16 intPanelNumber, Int32 intMargin) 
		{ 
			ChildObject = ctrl; 
			StatusBar = sb; 
			Panel = intPanelNumber; 
			Margin = intMargin; 
			ChildObject.Parent = StatusBar; 
			Resize(); 
			ChildObject.Visible = true; 
		}
		
		public void Resize() 
		{ 
			RECT Rectangle = new RECT(); 
			SendMessageA(StatusBar.Handle.ToInt32(), (int)SB_GETRECT, Panel, ref Rectangle); 
			ChildObject.Left = Rectangle.Left + Margin; 
			ChildObject.Top = Rectangle.Top + Margin; 
			ChildObject.Height = Rectangle.Bottom - Rectangle.Top - 2 * Margin; 
			ChildObject.Width = Rectangle.Right - Rectangle.Left - 2 * Margin; 
		}
	} // end class
} // end namespace


// ======================================
// Original vb code below
// ======================================

/*
' StatusBarChild class
'
' To put any object (a progressbar, a button...) in a statusbar panel in a VB.Net project
' E. Marcon, aug. 2004
' http://e.marcon.free.fr


Class StatusBarChild

    Public ChildObject As Object         ' The progressbar or any child control
    Public StatusBar As StatusBar        ' The statusbar
    Public Panel As Int16                ' The status panel
    Public Margin As Int32               ' The margin between the panel's edge and the progressbar


    ' API SendMaessageA in User32: returns the rectangle (RECT structure) used to display a status-bar panel
    Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Int32, ByVal msg As Int32, ByVal wParam As Int32, ByRef lParam As RECT) As Long
    Public Const WM_USER As Long = &H400
    Public Const SB_GETRECT As Long = (WM_USER + 10)
    ' RECT structure to get the panel's display rectangle
    Public Structure RECT
        Public Left As Int32
        Public Top As Int32
        Public Right As Int32
        Public Bottom As Int32
    End Structure


    Public Sub New(ByRef obj As Object, ByRef sb As StatusBar, Optional ByRef intPanelNumber As Int16 = 0, Optional ByVal intMargin As Int32 = 2)
        ' Puts a progress bar in a statusbar's panel

        ' Affects the progressbar to the class members
        ChildObject = obj
        StatusBar = sb
        Panel = intPanelNumber
        ' Sets the margin between the statusbar panel edge and the progressbar
        Margin = intMargin
        ' Reparent it
        ChildObject.Parent = StatusBar
        ' Set the size
        Resize()
        ' Set it visible
        ChildObject.Visible = True
    End Sub


    Public Sub Resize()
        'Fits  the child object to the status bar

        Dim Rectangle As RECT
        ' Use the API to get the panel's display rectangle
        SendMessage(StatusBar.Handle.ToInt32, SB_GETRECT, Panel, Rectangle)

        ' Resize
        With ChildObject
            .Left = Rectangle.Left + Margin
            .Top = Rectangle.Top + Margin
            .Height = Rectangle.Bottom - Rectangle.Top - 2 * Margin
            .Width = Rectangle.Right - Rectangle.Left - 2 * Margin
        End With
    End Sub

End Class
*/