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Marshal.GetActiveObject Method

.NET Framework 2.0

Other Versions

Obtains a running instance of the specified object from the Running Object Table (ROT).

Namespace: System.Runtime.InteropServices
Assembly: mscorlib (in mscorlib.dll)

Syntax

C++

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public static Object GetActiveObject (
	string progID
)

Copy

public static Object GetActiveObject (
	String progID
)

JScript

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public static function GetActiveObject (
	progID : String
) : Object

Parameters

progID: The ProgID of the object being requested.

Return Value

The object requested. You can cast this object to any COM interface that it supports.

Remarks

Marshal.GetActiveObject exposes the GetActiveObject COM API method from OLEAUT32.DLL; however, the latter expects a class identifier (CLSID) instead of the programmatic identifier (ProgID) expected by this method. To obtain a running instance of a COM object without a registered ProgID, use platform invoke to define the GetActivateObject COM method. For a description of platform invoke, see Consuming Unmanaged DLL Functions. For additional information about the GetActiveObject COM method, see the MSDN Library.

Note
This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

Note

This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

.NET Framework Security

SecurityPermission for permission to call unmanaged code. Associated enumeration: UnmanagedCode Security action: LinkDemand

Platforms

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

Version Information

.NET Framework

Supported in: 2.0, 1.1, 1.0

Reference

Marshal Class
Marshal Members
System.Runtime.InteropServices Namespace

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FAQ

Obtaining a running MS Office Excel,... instance.

The Office programms are register itself in the Running Object Table (ROT).

So you can try first to open it, and create only a new one if necessary.

Microsoft.Office.Interop.Excel.Application app=null;
try{
  app=(Microsoft.Office.Interop.Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
} catch(Exception){
  app=null;
}
if (app==null){
    app=new Microsoft.Office.Interop.Excel.Application();
    app.Visible=true;
}

Don't do this with MS Project! Project may wait for the Project Server account selection dialog or for the login dialog, and polling is a bad idea.

History

11/10/2006
flori