Develop Reference

How to get the main monitor window desktop area in Windows from a .NET5 app?

It sounds like there is a new way to call Windows API (instead of PInvoke): Calling Windows APIs in .NET5.
Is there a way to get all monitors definition (size++)? Having the main one (the number 1)? And get coordinates (top left and bottom right) of its WorkingArea (the available window space without the taskbar)?

I could be misreading the release, but I don't believe the approach has changed: you still use the same Windows Runtime (WinRT) APIs.
.NET5 applications can now access Windows APIs through a new set of Target Framework Monikers (TFMs), which have been extended to support platform specific APIs. This is the recommended mechanism for .NET going forward. For more information on this change, please refer to the .NET5 Preview 8 announcement.
This change means that applications targeting .NET5 no longer need to reference the Microsoft.Windows.SDK.Contracts NuGet package.
Developers can access this functionality by installing the latest preview for .NET5 (preview 8) and Visual Studio 16.8 (preview 2).
What has changed is the way you add references to these APIs to your project. Instead of including the Microsoft.Windows.SDK.Contracts NuGet package, you specify which operating systems/versions your project supports via Target Framework Monikers (TFMs). Adding a TFM for Windows automatically adds access to the appropriate WinRT APIs for the Windows version you specified.
There's a guide for this in the windows-uwp repo.
Modify a .NET project to use Windows Runtime APIs
There are several options for .NET projects:
Starting in .NET 5, you can add a Target Framework Moniker (TFM) to your project file to access WinRT APIs. This option is supported in projects that target Windows 10, version 1809 or later.
For earlier versions of .NET, you can install the Microsoft.Windows.SDK.Contracts NuGet package to add all necessary references to your project. This option is supported in projects that target Windows 10, version 1803 or later.
If your project multi-targets .NET 5 (or later) and earlier versions of .NET, you can configure the project file to use both options.
.NET 5 and later: Use the Target Framework Moniker option
This option is only supported in projects that use .NET 5 (or a later release) and target Windows 10, version 1809 or a later OS release. For more background info about this scenario, see this blog post.
With your project open in Visual Studio, right-click your project in Solution Explorer and choose Edit Project File. Your project file should look similar to this.
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>WinExe</OutputType>
<TargetFramework>net5.0</TargetFramework>
</PropertyGroup>
</Project>
Replace the value of the TargetFramework element with one of the following strings:
net5.0-windows10.0.17763.0: Use this value if your app targets Windows 10, version 1809.
net5.0-windows10.0.18362.0: Use this value if your app targets Windows 10, version 1903.
net5.0-windows10.0.19041.0: Use this value if your app targets Windows 10, version 2004.
For example, the following element is for a project that targets Windows 10, version 2004.
<TargetFramework>net5.0-windows10.0.19041.0</TargetFramework>
In later versions of .NET, you can replace the value with the relevant version, for example net6.0-windows10.0.19041.0.
Save your changes and close the project file.

Getting "NETSDK1045 The current .NET SDK does not support .NET Core 3.0 as a target" when using Blazor Asp.NetCore hosted template

I've installed the preview of .NetCore 3.0 and tried to run the blazor template Blazor (ASP.NET Core hosted) in Visual Studio 2019:
The error that occured, was the following:
NETSDK1045 The current .NET SDK does not support .NET Core 3.0 as a target. Either target .NET Core 2.2 or lower, or use a .NET SDK version that supports .NET Core 3.0.

During these days I had to overcome this issue on a number of different development machines/containers: eventually, I found no less than 6 different reasons that could cause this kind of error:
Missing .NET Core 3 SDK (x86 or x64)
.NET Core SDK preview support not enabled in VS2019
VS2017 instead of VS2019
Wrong SDK path in PATH environment variable(s)
Wrong SDK path in MSBuildSDKsPath environment variable(s)
Wrong SDK version in the project's global.json file
The workarounds for those scenarios are pretty easy to understand, you basically have to either install the proper SDK or remove the "offending" SDK reference(s). However, I did my best to document them all in this post on my blog.

Following this comment, I managed to resolve the problem by installing the x86 version of the .NET Core 3.0 additionally to the x64 version. The build worked after restarting Visual Studio (2019).

for me the solution was removing a path variable MSBuildSDKsPath - Because of exploring preview sdks's i at some point declared that variable to fix another sdk bug - seems like that force sets the used version. So in my case it was set to 3.0.100 and resulted in errors when attempting to use 3.1.300

I got the same error and resolve it with checking the option "Use previews of the .NET Core SDK (requires restart)".
Open Tools > Options and try looking at "Preview Features" or ".Net Core" depending of your Visual Studio version.
Watch out of VS updates, they can disable it.

This is a very hacky-feeling solution but at least it worked. Let's say you've installed the SDK for 3.0.100-rc1-014190. It shows up in dotnet --list-sdks as expected but still doesn't seem to be detected by Visual Studio, and you get the same NETSDK1405 error when trying to build or test anything from the dotnet CLI.
Look in your dotnet SDK install directory (usually C:\Program Files\dotnet\sdk). You should see your preview SDK in there. Either create a copy or rename the existing folder to remove the preview version suffix. For example 3.0.100-rc1-014190 would instead become 3.0.100, like so:
Doing this made .Net Core 3 preview support finally work in VS2019 Preview 4 and the dotnet CLI for me.

For me it was as simple as enabling the preview in Visual Studio 2019. Unfortunately most posts that show how to do this are I believe out of date. I finally came across this stack overflow post How to enable .NET Core 3 preview SDK in VS2019? They moved the check box and it was not on by default for me.

This was a frustrating issue to track down and after doing all of the updates to VS and still not being able to install I tracked it down to an environment variable. Try removing MSBuildSDKsPath and see if that fixes your issue.

ClickOnce Deployment .Net Framework 4.6.1 installation error

I have a clickonce application being tested on a virtual machine. This virtual machine is empty and my application requires .Net Framework 4.6.1 on the machine. Now, my application is able to install .Net 4.6.1 but I'm having a weird behavior after install. I'm receiving this message when the application is being open after the installation of .Net 4.6.1.
I added 4.6.1 on my prerequisite by following this guide. How to Create .Net Framework Prerequisites Entry in Microsoft Visual Studio 2015
Here's the message
When I try to run the setup again, the setup process goes through then it launches my application. It seems the setup cannot detect the framework installed right after it install it. Or something went wrong somewhere during the installation. Is there a way to handle this? Any suggestion will be appreciated. Thanks!

The error message says that your application requires CLR 4.0.xxxx. If you specify .NET 4.0 as requirement too ? Maybe you are trying to execute something developped with .NET 4.0 anyway. This could help you :
Backward compatibility and the .NET Framework 4.5 :
The .NET Framework 4.5 and its point releases are backward-compatible with apps that were built with earlier versions of the .NET Framework.In other words, apps and components built with previous versions will work without modification on the .NET Framework 4.5.However, by default, apps run on the version of the common language runtime for which they were developed, so you may have to provide a configuration file to enable your app to run on the .NET Framework 4.5.For more information, see the Version compatibility for apps section earlier in this article.
source

.NET Application is targeting 4.5, Setup.exe says it requires version 2.0.50727

I'm working on upgrading a windows application/service to target newer .NET frameworks for a client. This is the first time I've done anything of the sort. I changed the Target Framework in the C# project's properties window to 4.5, rebuilt the project without any errors, and then tried to run setup.exe. When I run this, it says:
This setup requires the .NET Framework version 2.0.50727.
Does anyone know why this would be happening? I read about launch conditions and that it could possibly be checking that the client computer requires v2.0, but I don't see an option to view the launch conditions in Visual Studio 2013.
Thanks

Dotnet 4.0 upgrade from 2.0

i am working on a dotnet C# web application which was initially created with VS 2003. My goal is to upgrade this application to Dotnet 4.0 without changing any functionaltiy. The solution has 9 projects (1 web + 8 Library projects). The Web project refers the 8 libraries in DLLs. To start off, I created a New project in VS2010 and added the all the Project files from the existing source code. Every time i add a project file to my solution, i was prompted with the Converison wizard and i completed the conversion wizard succesfully and now the solution works fine. After the conversion, i noticed that Except the "Web" project, other projects are converted to Dotnet 2.0 but not 4.0. My application runs without error if i run it locally using VS2010. My questions are
Why the Class libaray project did not upgrade to 4.0? Currently the
Web project is shows up as Dotnet 4.0 and Libaray projects shows up
as Dotnet 2.0.
Can i deploy the application to IIS 7.0 with the
Dotnet runtime of 4.0? Will the Dlls created in version 2.0 work if my application
uses Dotnet 4.0 runtime version?
Please help...

If your'e migrating now, why not move directly to Visual Studio 2012, instead of 2010?
Anyway, what you can do is open the project properties in each of your projects, and change the target framework to the .NET framework 4.0.
Then if you get any compilation error you can probably easily solve it individually. This should be relatively easy if your projects are not too big.
As for your specific questions:
The automatic conversion would only change the format of the solution/projects to be compatible with the new version Visual Studio. It shouldn't change the target framework but you can change that yourself.
Yes, assemblies targeting .NET 2.0 can be loaded and used from assemblies targeting .NET 4.0.

1) Upgrading the solution/projects file only upgrades it's format so you can open it in VS 2010. It will usually leave the targeted .NET setting at the previous value. These are two seperate things. The wonderful thing about VS 2010 is it let's you target whatever version of .NET you desire, so no longer do you need multiple version of VS installed to support differnt .NET versions. It didn't change the targetted .NET version because it leaves it up to you. You can change it under the project settings and recompile your library projects to regenerate the DLLs
2) You will need an application pool for .NET 4. .NET is backwards compatible in that a .NET 2.0 app can run on a machine with .net 4 installed. However, the application pool for 2.0 applications must be separate from 4.0 apps. So it's just a matter of putting the app under the right app pool.