wwDotnetBridge is a small library designed to make it easy to call .NET components from Visual FoxPro. By providing an easy mechanism for loading .NET components and calling them without requiring explicit COM registration of .NET components, it's easy to add .NET functionality to your applications. Interact with core .NET framework components, access system and free or commercial 3rd party libraries, or build and access your own .NET components and call them from FoxPro all without requiring COM registration.
wwDotnetBridge also provides a host of support features to make it possible to access .NET type features that FoxPro and COM alone do not natively support. For example, native COM interop cannot access components with multiple constructors, value types, static or generic members and types.
wwDotnetBridge can automatically convert some problem types and provides wrappers that allow access to most unsupported features. There's also a powerful ComArray class that makes it easy to interact and manipulate .NET arrays, lists and collections, and a ComValue class that lets you assign, access and pass .NET values without ever passing the native .NET value into FoxPro which allows you to access types that COM simply cannot directly access.
There are two versions of wwDotnetBridge, one for .NET Framework (1.0 - 4.8) and one for .NET Core (.NET Core 5.0+).
Supported Platforms are:
- .NET 4.6.2 Runtime or later (.NET Framework - wwDotnetBridge)
- .NET Core 5.0 Runtime and later (32 bit .NET Core - wwDotnetCoreBridge)
- Windows 7 and newer
- Windows Server 2008 R2 and newer
Typical steps for working with wwDotnetBridge are:
- Initialize the .NET Runtime during Startup
- Instantiate a wwDotnetBridge instance
- Use
.CreateInstance()to create .NET Objects - Use direct property and method access to call instance methods and access properties
- Use
.GetProperty(),.SetProperty()and.InvokeMethod()
to indirectly access problem types in .NET - Use Static versions of the intrinsic functions
Although not strictly required it's a good idea to initialize the .NET Runtime during application startup. This ensures that you're loading a specific version of .NET and another component can't load something different. Only one version of a given .NET Runtime can run be loaded and first load wins.
Somewhere in the startup of your application call InitializeDotnetVersion():
*** Load dependencies and add to Procedure stack
*** Make sure wwDotnetBridge.prg wwDotnetBridge.dll ClrHost.dll
*** are in your FoxPro path
DO wwDotnetBridge && Load library
InitializeDotnetVersion() && Initialize .NET RuntimeIf you get an Unable to CLR Instance error when creating an instance of wwDotnetBridge, there might be a permissions problem access the wwDotnetBridge.dll. Please see Unable to load CLR Instance for more info on how to fix this issue. Recent versions will attempt to automatically unblock the dll if permissions allow.
Then when you need to access wwDotnetBridge call GetwwDotnetBridge() to get a cached instance and use it to access .NET components:
*** Create or get cached instance of wwdotnetbridge
LOCAL loBridge as wwDotnetBridge, loHttp
loBridge = GetwwDotnetBridge()
*** Create a built-in .NET class and run a method
loHttp = loBridge.CreateInstance("System.Net.WebClient")
loHttp.DownloadFile("http://west-wind.com/files/MarkdownMonsterSetup.exe",
"MarkdownMonsterSetup.exe")
DO wwUtils
GoUrl(FULLPATH("MarkdownMonsterSetup.exe")) && run it
*** Load a custom .NET assembly
loBridge.LoadAssembly("CustomDotnet.dll")
*** Access a .NET component from the new assembly
loItem = loBridge.CreateInstance("Custom.Item")
*** Access properties directly
? loItem.Sku
loItem.Sku = "NewSku"
lnTotal = loItem.CalculateTotal()
*** Access non-accessible properties and methods indirectly
*** Non accessible might be: Value Type, Enum, Generic Type, Long, Guid etc.
lnFlagValue = loBridge.GetProperty(loItem,"Flag")
lnFlagValue = loBridge.SetProperty(loItem,"Flag",5)
loBridge.InvokeMethod(loItem,"PassFlagValue",lnFlagValue)
*** Access Static Properties and methods
lcDomain = loBridge.GetStaticProperty("System.Environment","UserDomainName")
llOnline = loBridge.InvokeStaticMethod("System.Net.NetworkInformation.NetworkInterface",;
"GetIsNetworkAvailable")
*** Array Result Fixups
loComArray = loBridge.InvokeMethod(loItem,"GetDetailItems",lnPk) && returns object array
FOR lnX = 1 to loComarray.Count
loLineItem = loComArray.Item[lnX]
? loLineItem.Sku + " " + loLineItem.Descript
ENDFOR
*** Pass an Array
loItems = loBridge.CreateArray("MyApp.LineItem")
loItem = loBridige.CreateInstance("MyApp.LineItem")
loItem.Sku = "XXXX"
loItem.Descript = "New Item"
loItems.AddItem(loItem)
loBridge.InvokeMethod(loInvoice,"AddItems",loItems)wwDotnetBridge provides the following enhancements over plain COM Interop:
- Access most .NET Components directly even those not marked [ComVisible]
- Requires no COM Registration
- Call any .NET method and set and get properties
- Call any .NET method asynchronously and get called back on completion
- Instantiate types with parameterized constructors
- Call overloaded methods using standard method names
- Support for many natively unsupported .NET types and values
- Access Static members, Value/Struct types, Generics, Binary, Guids, DbNulls
- Automatically fix up problematic .NET Types on method returns
- Provides easy Array, List and Collection access via ComArray wrapper
- ComValue helper can store results and parameters in .NET
- ComValue works around .NET and COM type conversions issues
- Multi-threading library built-in
- wwDotnetBridge can also work with regular COM Interop (w/o runtime hosting)
This library consists of 3 components (all provided in source):
- ClrHost.dll - Win32 Loader for the .NET Runtime
- wwDotnetBridge.dll - .NET assembly Proxy and Helper
- wwDotnetBridge.prg - FoxPro front end to .NET Proxy
Make sure CrlHost.dll (or wwIpstuff.dll for commercial West Wind tools) and wwDotnetBridge are accessible via the FoxPro path. Ideally you'll want to have these DLLs in your current executing path of the application - typically the root folder of the application.
If you're using FoxPro you can simply use the wwDotnetBridge.prg class to load an assembly and fire away at it or access existing .NET components directly.
This example loads the OpenPop .NET library and accesses a POP3 mailbox to display messages waiting:
*** Load library and initialize wwDotnetBridge
do wwDotNetBridge
LOCAL loBridge as wwDotNetBridge
loBridge = CreateObject("wwDotNetBridge")
*** Load an assembly from disk
loBridge.LoadAssembly("bin\OpenPop.dll")
*** Create an instance of a class - note: No COM registration
loPop = loBridge.CreateInstance("OpenPop.Pop3.Pop3Client")
*** This won't work due to overloads
* loPop.Connect("mail.server.net",587,.f.)
*** So, call indirectly instead
? loBridge.InvokeMethod(loPop,"Connect","mail.server.net",110,.f.)
*** Most methods/members do work directly
? loPop.Authenticate("jb007","seekrit")
lnCount = loPop.GetMessageCount()
? StringFormat("{0} Messages",lnCount)
*** NOTE: OpenPop is 1 based because pop3 is 1 based!
** show last messages
FOR lnX = lnCount TO 1 STEP -1
loHeader = loPop.GetMessageHeaders(lnx)
? loHeader.From.DisplayName
? " " + loHeader.Subject
?
IF lnX < lnCount - 10
EXIT
ENDIF
ENDFORThe example demonstrates a few simple features: Loading an assembly, creating a .NET type instance and then calling methods and accessing properties either directly or indirectly. You can call Static methods and access static members.
For many methods and properties on .NET object references you can directly access the members, but some members are not directly callable via COM if there are overloads on a method, if there are Generics, enums or Value Types involved in the method or member access. It's best to always try direct access first and if that fails attempt to use indirect access to the wwDotnetBridge instance.
In that case you can use indirect referencing to access members with:
- loBridge.InvokeMethod(instance,"Method",parm1,parm2..,parm15)
- loBridge.GetProperty(instance,"Property")
- loBridge.SetProperty(instance,"Property",valueToSet)
Nested hierarchies can also be accessed for child properties or arrays:
- loBridge.GetProperty(instance,"Property.SubProperty")
- loBridge.GetProperty(instance,"Property.ArrayProp[0]")
These methods internally use Reflection to call .NET code, but because they run inside of .NET they can do many things that native COM interop cannot due to the limitations for type marshalling over COM and the incompatibilities of the FoxPro type system.
Here's another example that demonstrates a few more features including calling static methods and setting enum values and accessing collections using enumerators.
*** Load library
DO wwDotNetBridge
*** Create instance of wwDotnetBridge
LOCAL loBridge as wwDotNetBridge
loBridge = CreateObject("wwDotNetBridge","V4")
loStore = loBridge.CreateInstance("System.Security.Cryptography.X509Certificates.X509Store")
? loBridge.cErrorMsg
*** Grab a static Enum value
leReadOnly = loBridge.GetEnumvalue("System.Security.Cryptography.X509Certificates.OpenFlags.ReadOnly")
*** Use the enum value
loStore.Open(leReadOnly) && 0 - if value is known
*** Returns a .NET Collection of store items
laCertificates = loStore.Certificates
*** Collections don't work over regular COM Interop
*** so use indirect access
lnCount = loBridge.GetProperty(laCertificates,"Count")
*** Loop through Certificates
FOR lnX = 0 TO lnCount -1
*** Access collection item indirectly using extended syntax
*** that supports nested objects and array/collection [] brackets
LOCAL loCertificate as System.Security.Cryptography.X509Certificates.X509Certificate2
loCertificate = loBridge.GetPropertyEx(loStore,"Certificates[" + TRANSFORM(lnX) + "]")
IF !ISNULL(loCertificate)
? loCertificate.FriendlyName
? loCertificate.SerialNumber
? loCertificate.GetName()
*? loBridge.GetPropertyEx(loCertificate,"IssuerName.Name")
ENDIF
ENDFORYou can also call any .NET method asynchronously and get called back when the method has completed executing:
DO wwDotnetBridge
LOCAL loBridge as wwDotnetBridge
loBridge = GetwwDotnetBridge("V4")
loHttp = loBridge.CreateInstance("System.Net.WebClient")
*** Create a callback object - object has to be 'global'
*** so it's still around when the callback returns
*** Use Public or attach to long lived object like form or _Screen
PUBLIC loCallback
loCallBack = CREATEOBJECT("HttpCallback")
*** Make the async call - returns immediately
loBridge.InvokeMethodAsync(loCallback, loHttp, ;
"DownloadData",;
"http://west-wind.com/files/HelpBuilderSetup.exe")
? "Download has started... running in background."
RETURN
*** Callback class
DEFINE CLASS HttpCallback as Custom
FUNCTION OnCompleted(lvResult, lcMethod)
? "Http Call completed"
? "Received: " + TRANS(LEN(lvResult),"999,999,999")
lcFile = ADDBS(SYS(2023)) + "HelpBuilderSetup.exe"
*** Write to file to temp folder
STRTOFILE(lvResult,lcFile)
*** Launch the downloaded installer
TRY
*** Open the Zip file
DO wwutils
GoUrl(lcFile)
CATCH
ENDTRY
ENDFUNC
FUNCTION OnError(lcErrorMessage, loException, lcMethod)
? lcErrorMessage
ENDFUNC
ENDDEFINE.NET delegates and events are not directly supported. If the .NET object is available as a registered COM object, the COM events which translate to native FoxPro events; COM event binding is separate from wwDotNetBridge.
wwDotNetBridge supports an alternative approach to obtain events without COM registration. You can subscribe to all events of a .NET object by calling wwDotNetBridge.SubscribeToEvents. You pass the source object for the events and your handler object. The class for your handler object should have an On... function for each event.
This example creates a System.Net.Mail.SmtpClient object and handles its one event, SendCompleted:
LOCAL loSmtpClient, loSmtpHandler, loSmtpEventSubscription
loSmtpClient = loBridge.CreateInstance("System.Net.Mail.SmtpClient")
loSmtpHandler = CREATEOBJECT("MySmtpEventHandler")
loSmtpEventSubscription = loBridge.SubscribeToEvents(loSmtpClient, loSmtpHandler)
* Send email here
DEFINE CLASS MySmtpEventHandler as Custom
PROCEDURE OnSendCompleted(loSender, loEventArgs)
* Handle the event here
ENDPROC
ENDDEFINEWhen no longer want to be notified of the events, call Unsubscribe on the subscription (loSmtpEventSubscription in this example).
The following people/organizations have provided sponsorship to this project by way of direct donations or for paid development as part of a development project using these tools:
wwDotnetBridge was originally developed for West Wind Client Tools and West Wind Web Connection, which continue to include a slightly modified version of wwDotnetBridge. West Wind Technologies has kindly open sourced wwDotnetBridge to extend the reach of FoxPro just a bit longer by allowing easy integration with .NET and allowing more people to access this useful functionality.
wwDotnetBridge updates are initially developed for both of the commercial products with any changes merged into this project when changes are made. The commercial versions also include a few add-on features used by the products such as an SMTP client, SFTP support, Encryption and Image management utilities through .NET wrappers. If you want a fully supported version of wwDotnetBridge or would like to sponsor further development efforts on wwDotnetBridge, you can show your support by purchasing a license for either of these products.
Craig offered early support and feedback for this project and billed project time for a number of additions to the library as part of a larger project.
Bill provided a sizable donation to the project and valuable feedback for a host of improvements and bug fixes.
Sunil required a number of custom integrations into their FoxPro product that resulted in discovery of a number of edge cases that ended up getting integrated into wwDotnetBridge. WeatherTrend kindly donated a chunk of billable time to adding a handful of these small features.
Want to sponsor this project, need customization or want make a donation to show your support? You can contact me directly at rstrahl@west-wind.com or you can also make a donation online via PayPal.
- Sponsor this GitHub account
- Make a donation for wwDotnetBridge using PayPal
- Make a donation for wwDotnetBridge using our Web Store
- Purchase a license for West Wind Internet and Client Tools
This library is licensed under MIT license terms:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
© 2012-2018 Rick Strahl, West Wind Technologies
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
© 2012-2023 Rick Strahl, West Wind Technologies
