DotNetBrowser-Examples/vbnet/console/JavaScriptBridge.Promises/Program.vb at v4 · TeamDev-IP/DotNetBrowser-Examples · GitHub

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#Region"Copyright"

'' Copyright © 2026, TeamDev. All rights reserved.
''
'' Redistribution and use in source and/or binary forms, with or without
'' modification, must retain the above copyright notice and the following
'' disclaimer.
''
'' THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
'' "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
'' LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
'' A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
'' OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
'' SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
'' LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
'' DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
'' THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
'' (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
'' OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#EndRegion

ImportsSystem.Text
ImportsSystem.Threading.Tasks
ImportsDotNetBrowser.Browser
ImportsDotNetBrowser.Engine
ImportsDotNetBrowser.Geometry
ImportsDotNetBrowser.Js
ImportsJavaScriptBridge.Promises

''' <summary>
''' This example demonstrates how to work with JavaScript Promises
''' via JS-.NET bridge.
''' </summary>
FriendClassProgram

PublicSharedSubMain()
UsingengineAsIEngine=EngineFactory.Create()
UsingbrowserAsIBrowser=engine.CreateBrowser()

browser.Size=NewSize(700,500)
DimhtmlBytes()AsByte=Encoding.UTF8.GetBytes("<html>
<body>
<scripttype=''text/javascript''>
functionCreatePromise(success)
{
returnnewPromise(function(resolve,reject){
if(success){
resolve(''Promise fulfilled.'');
}
else{
reject(''Promise rejected.'');
}
});
};
</script>
</body>
</html>")

browser.Navigation.LoadUrl("data:text/html;base64,"&Convert.ToBase64String(htmlBytes)).Wait()
DimwindowAsIJsObject=browser.MainFrame.ExecuteJavaScript(OfIJsObject)("window").Result

'' Prepare promise handlers.
DimpromiseResolvedHandlerAsAction(OfObject)=Sub(o)Console.WriteLine($"Success: {o}")
DimpromiseRejectedHandlerAsAction(OfObject)=Sub(o)Console.Error.WriteLine($"Error: {o}")

'' Create a promise that is fulfilled.
Console.WriteLine("Create a promise that is fulfilled...")
Dimpromise1=window.Invoke(OfIJsObject)("CreatePromise",True)
'' Append fulfillment and rejection handlers to the promise.
promise1.Invoke("then",promiseResolvedHandler,promiseRejectedHandler)

'' Create a promise that is rejected.
Console.WriteLine("Create a promise that is rejected...")
Dimpromise2=window.Invoke(OfIJsObject)("CreatePromise",False)
'' Append fulfillment and rejection handlers to the promise.
promise2.Invoke("then",promiseResolvedHandler,promiseRejectedHandler)

CreatePromiseAsync(window).Wait()
EndUsing
EndUsing

Console.WriteLine("Press any key to terminate...")
Console.ReadKey()
EndSub

'' #docfragment "JavaScriptBridge.Promises.Async"
PrivateSharedAsyncFunctionCreatePromiseAsync(ByValwindowAsIJsObject)AsTask
'' IJsPromise can be integrated with async/await using TaskCompletionSource.

'' Create a promise that is fulfilled.
Console.WriteLine($"{vbLf}Create another promise that is fulfilled...")
DimtcsAsNewTaskCompletionSource(OfObject)(TaskCreationOptions.RunContinuationsAsynchronously)
Dimpromise3AsIJsPromise=window.Invoke(OfIJsPromise)("CreatePromise",True)
promise3.Then(
Sub(o)
Console.WriteLine($"Callback:Success: {o}")
tcs.SetResult(o)
EndSub,
Sub(e)tcs.SetException(NewException(e?.ToString())))
Dimresult=Awaittcs.Task
Console.WriteLine($"Result: {result}")

'' Create a promise that is rejected.
Console.WriteLine($"{vbLf}Create another promise that is rejected...")
Dimtcs2AsNewTaskCompletionSource(OfObject)(TaskCreationOptions.RunContinuationsAsynchronously)
Dimpromise4AsIJsPromise=window.Invoke(OfIJsPromise)("CreatePromise",False)
promise4.Then(
Sub(o)tcs2.SetResult(o),
Sub(e)
Console.WriteLine($"Callback:Error: {e}")
tcs2.SetResult(Nothing)
EndSub)
Awaittcs2.Task
EndFunction
'' #enddocfragment "JavaScriptBridge.Promises.Async"

EndClass