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dotnet publish error - The "TransformWebConfig" task failed unexpectedly.

When trying to publish an ASP.NET Core web application through the dotnet publish command on our build server, it failed with the following error message:

C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: The "TransformWebConfig" task failed unexpectedly. [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: System.Exception: In process hosting is not supported for AspNetCoreModule. Change the AspNetCoreModule to at least AspNetCoreModuleV2. [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: at Microsoft.NET.Sdk.Publish.Tasks.WebConfigTransform.SetAspNetCoreHostingModel(String aspNetCoreHostingModelValue, String aspNetCoreModuleName, XElement aspNetCoreElement) [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: at Microsoft.NET.Sdk.Publish.Tasks.WebConfigTransform.Transform(XDocument webConfig, String appName, Boolean configureForAzure, Boolean useAppHost, String extension, String aspNetCoreModuleName, String aspNetCoreHostingModel, String environmentName, String projectFullPath) [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: at Microsoft.NET.Sdk.Publish.Tasks.TransformWebConfig.Execute() [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] C:\Program Files\dotnet\sdk\7.0.201\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [D:\b\3\_work\222\s\SOFACore\Example\eShopExample\eShopExample.csproj] ##[error]Error: The process 'C:\Program Files\dotnet\dotnet.exe' failed with exit code 1

What is the issue?

The dotnet publish command will apply a web.config transformation as part of the web deploy. This transformation fails because the web.config is not correct to be used with an in process ASP.NET Core application.

Here is our incorrect web.config file:

Notice the AspNetCoreModule value for the module attribute. That explains the following error:

In process hosting is not supported for AspNetCoreModule. Change the AspNetCoreModule to at least AspNetCoreModuleV2.

To fix this, we have to update our web.config and set the module attribute correctly to AspNetCoreModuleV2:

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