ASP.NET Core 2.2 -> 3.0 upgrade. env.IsDevelopment() not found

Question

I upgraded an existing 2.2 project to 3.0. I copied the new code for Program/Startup from a new 3.0 project to my existing 2.2 project. It worked, but the IsDevelopment() below:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } }

Results in this error:

'IWebHostEnvironment' does not contain a definition for 'IsDevelopment' and the best extension method overload 'HostingEnvironmentExtensions.IsDevelopment(IHostingEnvironment)' requires a receiver of type 'IHostingEnvironment'

The same line did not caused a newly created 3.0 project. What do I need to modify/add to the project upgraded from 2.2?

What about blessed vegetables?

ruffin
– ruffin

2023-04-27 21:45:18 +00:00
Commented Apr 27, 2023 at 21:45 — ruffin
– ruffin, Commented Apr 27, 2023 at 21:45

Rena · Accepted Answer · 2019-09-24 01:48:50Z

261

The new IHostEnvironment, IsDevelopment, IsProduction etc. extension methods are in the Microsoft.Extensions.Hosting namespace which may need to be added to your app.

Reference:

https://learn.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.0&tabs=visual-studio#migrate-startupconfigure

https://github.com/aspnet/AspNetCore/issues/7749

answered Sep 24, 2019 at 1:48

Rena

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3 Comments

Luke Over a year ago

No need to install the Microsoft.Extensions.Hosting package, just add the using statement as mentioned in @Greg's post.

Macindows Over a year ago

so then we need both Microsoft.Extensions.Hosting and using Microsoft.AspNetCore.Hosting; at the same time... Wonder how that works? Class name from one package but its method from another?

Rena Over a year ago

Actually,the asp.net core 3.0 do not have such issue now.It has been fixed.

Omu · Accepted Answer · 2019-12-07 09:48:50Z

151

As Rena says IsDevelopment has been moved to IHostEnvironment Interface in the Microsoft.Extensions.Hosting Namespace

I just had to add the

using Microsoft.Extensions.Hosting;

and then I could use IsDevelopment() as before.

edited Dec 7, 2019 at 9:48

Omu

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answered Sep 24, 2019 at 2:05

Greg

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2 Comments

PatsonLeaner Over a year ago

Thanks a million, this answer helped me to solve the exception. Was migrating asp.net core 23.0 to core 3.1. just add this library and all worked like sharp. Billiant!

Mmm Over a year ago

Fast forward 5 years and this is still helpful with .Net 8.

Alison Horacio · Accepted Answer · 2021-06-07 01:28:26Z

int the extension:

using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.Hosting; public static class HostingEnvironmentExtensions { public static IConfigurationRoot GetAppConfiguration(this IWebHostEnvironment env) { return AppConfigurations.Get(env.ContentRootPath, env.EnvironmentName, env.IsDevelopment()); } }

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