Clicking a Button in Another Application

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Update: For Windows 10 (and I assume Windows 8 and above) the Windows Calculator Accesssory cannot be used for this. See the modification of the attached sample code necessary for the Windows Character Map Accessory for the ButtonId and fn.

This article provides a simple sample of an application that clicks a button in another application. The technique could be used for other controls too. For the purpose of a simple sample the program is a console program. The sample will click the "=" button in the Windows Calculator Acesssory or can click the "Select" button for the Windows Charactrer Map Acesssory.

This article was originally dwritten using Windows 7 but the Windows Calculator Acesssory in Windows 10 (and I assume Windows 8 and above) cannot be used in the manner it is used here.

The first thing to do is to determine what button to click and the circumstances of when to click it. Execute the Windows Calculator Acesssory or Windows Charactrer Map Acesssory.

For the Windows Calculator Acesssory type "2+2=" into it. The result should be 4 of course. Then click the "=" button. Each time "=" is clicked, the value will be increased by 2. So that is something very simple to automate. We can "manually" execute Calculator and type "2+2=" into it. Then when we execute our sample application it can just click the "=" button and we can see the result.

For the Windows Charactrer Map Acesssory, we just need to execute it. When the "Select" button is clicked the characer is put into the selected box. We canmove to a different character usign the mouse or keyboard. We can see that the "Select" button is clicked becasue the specified character is put into the selected box.

The next thing to do is to determine the identity of the button to be clicked so our program can click it. With the acesssory executing, go to Visual Studio. In the "Tools" menu is "Spy++". If your system is a 64-bit system then you need to use the 64-bit version of Spy++. The Spy++ toolbar will look like:

Spy++ toolbar

Click on the "Find Window" icon; it is a binoculars with a window in the top-left; it looks like: "Find Window" icon

That will open a "Find Window" dialog. Now first, ensure that the acesssory is visible; at least the relevant button part of it. Then click on the "Finder Tool" icon (the square with a circle in it that looks like a target). The "Find Window" dialog looks like:

"Find Window" dialog

With the mouse button down, drag from the Finder Tool icon to the "=" button and release the mouse. The Find Window dialog will be filled in with the button's handle and other data. Click on "OK". You will then get a "Window Properties" window with a tab control with 5 tabs. The five tabs are General, Styles, Windows, Class and Process. The wndow will look like:

"Window Properties" window

Look for "Contol ID" near the botom of the first (General) tab. It will probably have the value "00000079" for the Windows Calculator Acesssory or "00000067" for the Windows Charactrer Map Acesssory. It is a hexadecimal value. Whatever the value is, it will probably be that value every timne you execute that program. At the Windows API level, controls are often identified by a control id. We can use the Contol ID shown in the Window Properties window in our program.

We are ready to write the application. I assume you can create a console application. If your system is 64-bit then you will need to change the "Platform Target" to "x64". The .Net Process class cannot do everything we need it to do when our application is not the same as the other application in terms of bits (32-bits and 64-bits). The "Platform Target" property is in the Build tab of the project's properties. If you need to automate a 32-bit application from a 64-bit application or 64-bit from 32-bit then you can do that but you will need to use the Windows API directly to do the equivalent of what we are using the .Net Process class to do.

You need to add a "using" for the "System.Diagnostics" and "System.Runtime.InteropServices" namespaces. You will also need to add the following to the "Program" class:

const int WM_COMMAND = 0x0111;
const int BN_CLICKED = 0;
const int ButtonId = 0x79;
const string fn = @"C:\Windows\system32\calc.exe";

static extern IntPtr GetDlgItem(IntPtr hWnd, int nIDDlgItem);

static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, IntPtr lParam);

For the Windows Charactrer Map Acesssory use the following for the ButtonId and fn:

 const int ButtonId = 0x67;
const string fn = @"C:\Windows\system32\charmap.exe";

The sample program will first look at the processes to find Calculator. We will assume the exe is at:


The Windows Charactrer Map Acesssory is at:


When we find a process that is executed from there, we know for sure it is the one we are looking for. Note that there are very many processes in a system; many more than most people are aware of. Each Windows Service is a process. Windows Services and other processes that we need to ignore do not have a window, so we can ignore all processes without a window. The following code will do all that:

IntPtr handle = IntPtr.Zero;
Process[] localAll = Process.GetProcesses();
foreach (Process p in localAll)
if (p.MainWindowHandle != IntPtr.Zero)
ProcessModule pm = GetModule(p);
if (pm != null && p.MainModule.FileName == fn)
handle = p.MainWindowHandle;
if (handle == IntPtr.Zero)
Console.WriteLine("Not found");

The GetModule function is shown later in this article.

We are ready to click the button from within our application. To click the button we will send a BN_CLICKED notification message to the button's parent, the Calculator main window. To do that we will need both the button id (as in the preceding) and the handle of the button. The handle varies for each execution but we can determine the handle based on the handle of its parent and the control id. The Windows API function GetDlgItem does that, as in:

IntPtr hWndButton = GetDlgItem(handle, ButtonId);

Windows messages are sent to a window as determined by the window handle. Messages also have a message id that specifies what the message is for. We will send a WM_COMMAND message. The other two parameters we need to send the message is a wParam and a lParam. The value of those depend on what the message is (the message id). For a WM_COMMAND message doing what we are doing, the control id is passed as the high word of wParam and the low word of wParam is the notification code (BN_CLICKED). The lParam is the handle of the control. It seems unnecessary to pass both the control id and the control window's handle but that is the way it works. The following sends the message:

int wParam = (BN_CLICKED << 16) | (ButtonId & 0xffff);
SendMessage(handle, WM_COMMAND, wParam, hWndButton);

When the processes are being searched, since some modules might be restricted from access for security purposes, we catch errors using the GetModule function. It is very simple, as in the following:

private static ProcessModule GetModule(Process p)
	ProcessModule pm = null;
	try { pm = p.MainModule; }
		return null;
	return pm;

To test the program, first execute Calculator and type in "2+2=". Then execute the sample program. Every time it executes, 2 will be added to the Calculator value.

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