Questions tagged [.net-core]
.NET Core is an open-source successor of the .NET Framework. It can be used in a wide variety of applications and verticals, ranging from servers and data centers to apps and devices. .NET Core is supported by Microsoft on Windows, Linux and macOS.
.net-core
45,031
questions
145
votes
17
answers
159k
views
Is it possible to make desktop GUI application in .NET Core?
I have been developing Windows Forms programs for few years. I am now looking into .NET Core (including ASP.NET Core MVC). I am searching for the new GUI desktop technology. In Visual Studio 2015 ...
- 3,879
144
votes
17
answers
229k
views
Entity Framework Core: `SqlNullValueException: Data is Null.` How to troubleshoot?
I am using Entity Framework Core in an ASP.NET Core application and Controller action and I haven't changed something to the working code nor to the database but I can't tell what is the query ...
- 8,533
144
votes
5
answers
68k
views
How to consume a Scoped service from a Singleton?
How should I inject (using .NET Core's built-in dependency injection library, MS.DI) a DbContext instance into a Singleton? In my specific case the singleton is an IHostedService?
What have I tried
I ...
- 75.6k
141
votes
11
answers
94k
views
How to mock IConfiguration.GetValue
I tried in vain to mock a top-level (not part of any section) configuration value (.NET Core's IConfiguration). For example, neither of these will work (using NSubstitute, but it would be the same ...
- 4,457
141
votes
3
answers
83k
views
.NET Core doesn't know about Windows 1252, how to fix?
This program works just fine when compiled for .NET 4 but does not when compiled for .NET Core. I understand the error about encoding not supported but not how to fix it.
Public Class Program
...
- 42k
140
votes
14
answers
138k
views
What replaces WCF in .Net Core?
I am used to creating a .Net Framework console application and exposing a Add(int x, int y) function via a WCF service from scratch with Class Library (.Net Framework). I then use the console ...
- 2,897
139
votes
6
answers
128k
views
How to extract a list from appsettings.json in .net core
I have an appsettings.json file which looks like this:
{
"someSetting": {
"subSettings": [
"one",
"two",
"three"
]
}
}
When I build my ...
- 15.7k
138
votes
5
answers
231k
views
Where is NuGet.Config file located in Visual Studio project?
I am wondering where is NuGet.Config file located in Visual Studio 2017 project? I tried to create my own NuGet.Config file in the root of the project, but I didn't find any new repositories (NuGet ...
- 15.7k
136
votes
5
answers
83k
views
Why does aspnet core start on port 80 from within Docker?
TL;DR: Why does an aspnet core app run on port 80 from within a Docker image, but 5000 outside a docker image.
Elaborate
I went through the aspnet core / docker tutorial found here:
https://learn....
- 5,334
135
votes
3
answers
75k
views
How to call ThenInclude twice in EF Core?
I'm creating an ASP.NET Core API app, and relying on EF Core. I have entities defined like this:
public class AppUser : IdentityUser
{
public string FirstName { get; set; }
public string ...
- 3,044
134
votes
3
answers
64k
views
I'm lost. What happened to ASP.NET MVC 5?
I've been keeping my head down working on various projects and apparently Microsoft has been busy making some big changes and it's confusing the hell out of me. ASP.NET Core first came onto my radar ...
- 12.9k
132
votes
11
answers
117k
views
Upload files and JSON in ASP.NET Core Web API
How can I upload a list of files (images) and json data to ASP.NET Core Web API controller using multipart upload?
I can successfully receive a list of files, uploaded with multipart/form-data ...
- 2,322
130
votes
12
answers
146k
views
dotnet: command not found in Mac
So I downloaded NET Core 2.1 SDK for mac and installed it. But when I run the dotnet command from terminal it throws -bash: dotnet: command not found error.
I am trying to use the dotnet new react ...
- 6,105
130
votes
22
answers
154k
views
Detected package downgrade warning (dotnet core, vs 2017)
I have just updated all my nuget packages for my solution (dotnet core 1.1 project).
I am now getting the following warnings and I don't really know what they mean.
Update: I am still getting ...
- 3,123
130
votes
3
answers
49k
views
Are async console applications supported in .NET Core?
At some point in time the CoreCLR supported async main entry points. See http://blog.stephencleary.com/2015/03/async-console-apps-on-net-coreclr.html
However both the following programs are not ...
- 16.3k
129
votes
19
answers
173k
views
Error NU1605 Detected package downgrade
I am experiencing the following NU1605 dependency errors in my netcoreapp2.0 console application:
NU1605 Detected package downgrade: System.Diagnostics.Debug from 4.3.0 to 4.0.11. Reference the ...
- 39.3k
128
votes
26
answers
296k
views
How to change the port number for Asp.Net core app?
I added the following section in project.json.
"commands": {
"run": "run server.urls=http://localhost:8082",
"web": "Microsoft.AspNet.Hosting --server Microsoft.AspNet.Server.Kestrel --...
- 28.3k
127
votes
24
answers
175k
views
MSBUILD throws error: The SDK 'Microsoft.NET.Sdk' specified could not be found
I'm trying to build a solution using msbuild command line and I keep getting this error:
error MSB4236: The SDK 'Microsoft.NET.Sdk' specified could not be found.
The version of msbuild is the latest ...
- 1,291
126
votes
7
answers
133k
views
Switch between dotnet core SDK versions
I recently installed VS 2017 RC and then automatically my dotnet version pointed to 1.0.0-preview4-004233. Due to that whenever I create a new project using command dotnet new -t Console I cannot see ...
- 2,564
126
votes
4
answers
104k
views
.NET Core IServiceScopeFactory.CreateScope() vs IServiceProvider.CreateScope() extension
My understanding is that when using the built in the dependency injection, a .NET Core console app will require you to create and manage all scopes yourself whereas a ASP.NET Core app will create and ...
- 1,261
125
votes
14
answers
122k
views
How to load appsetting.json section into Dictionary in .NET Core?
I am familiar with loading an appsettings.json section into a strongly typed object in .NET Core Startup.cs. For example:
public class CustomSection
{
public int A {get;set;}
public int B {get;...
- 9,986
123
votes
3
answers
73k
views
'ConfigurationBuilder' does not contain a definition for 'AddJsonFile'
I have the following error:
Program.cs(15,72): error CS1061: 'ConfigurationBuilder' does not contain a definition for 'AddJsonFile' and no accessible extension method 'AddJsonFile' accepting a first ...
- 33.3k
123
votes
6
answers
51k
views
No AppDomains in .NET Core! Why?
Is there a strong reason why Microsoft chose not to support AppDomains in .NET Core?
AppDomains are particularly useful when building long running server apps, where we may want to update the ...
- 1,279
122
votes
6
answers
168k
views
How to set json serializer settings in asp.net core 3?
json serializer settings for legacy asp.net core applications were set by adding AddMvc().AddJsonOptions(), but I don't use AddMvc() in asp.net core 3. So how can I set global json serialization ...
- 2,626
121
votes
3
answers
175k
views
How to use SqlClient in ASP.NET Core?
I am trying to use SQLClient library in the ASP.net Core but cant seem to get it working. I found this article online advising how to setup but its not working for me: http://blog.developers.ba/using-...
- 6,969
121
votes
2
answers
20k
views
On IServiceProvider what are the differences between the GetRequiredService and GetService methods?
What are the differences between IServiceProvider.GetRequiredService() and IServiceProvider.GetService()?
When is it a better idea to use GetRequiredService()?
- 1,789
121
votes
7
answers
213k
views
How to get an instance of IServiceProvider in .NET Core?
IServiceProvider is an interface with single method:
object GetService(Type serviceType);
It's used to create instances of types registered in .NET Core native DI container.
An instance of ...
- 17.8k
121
votes
25
answers
154k
views
The library hostpolicy.dll was not found
I have a simple .NET Core project (console app) that I'm trying to compile and run. dotnet build succeeds, but I get the following error when I do dotnet run:
dotnet run
Project RazorPrecompiler (....
- 52.3k
119
votes
13
answers
455k
views
The SSL connection could not be established
I am using a third party library (Splunk c# SDK ) in my ASP.NET core application. I am trying to connect to my localhost Splunk service via this SDK, but I get an exception saying:
System.Net....
- 1,291
119
votes
4
answers
139k
views
System.ServiceModel not found in .NET Core project
I have a .NET Core xUnit project. I'm trying to call a WCF service from it but get the following exception:
System.InvalidOperationException occurred
HResult=0x80131509
Message=An error occurred ...
- 28k
119
votes
2
answers
130k
views
Entity framework EF.Functions.Like vs string.Contains
I was reading the announcement of entity framework core 2.0 https://blogs.msdn.microsoft.com/dotnet/2017/08/14/announcing-entity-framework-core-2-0/
It says that they added new Sql functions like EF....
- 5,008
118
votes
4
answers
34k
views
"The project 'Web' must provide a value for Configuration" error after migrating to .NET Core 3
I've migrated an ASP.NET Core 2.2 project to Core 3.0 and am getting the error:
The project [Project location] must provide a value for Configuration.
There's not really a lot to go on with that ...
- 29.1k
118
votes
6
answers
85k
views
Dependency Injection with classes other than a Controller class
At this point I'm injecting things into my Controllers with ease, in some cases building my own ResolverServices class. Life is good.
What I cannot figure out how to do is get the framework to ...
- 5,013
117
votes
39
answers
259k
views
EF Core add-migration Build Failed
I have a developer that is getting "Build failed." when running add-migration in a .NET Core EF project, with no explanation of why the build failed. How do you troubleshoot this error?
This is what ...
- 1,789
116
votes
22
answers
165k
views
IIS: Handler "aspNetCore" has a bad module "AspNetCoreModuleV2" in its module list
I used angular .net core 2.2 template to build an application. In localhost working fine, When I host to IIS I'm getting this error. I'm using IIS 10 to host the application.
Error,
HTTP Error 500.21 -...
- 1,595
116
votes
1
answer
45k
views
.NET Core - When to use "dotnet new sln"
I'm a bit confused - the majority of .NET Core tutorials I have been reading have not mentioned "dotnet new sln" - they always just create the projects separately without any solution file to link ...
- 2,223
115
votes
14
answers
115k
views
Cannot find command 'dotnet ef'
I am using .NET Core 2.0 on Arch Linux / Visual Studio Code and am trying to get EF tools to work, but I keep getting the error:
cannot find command dotnet ef
I've just about looked everywhere and ...
- 1,525
115
votes
12
answers
97k
views
Return View as String in .NET Core
I found some article how to return view to string in ASP.NET, but could not covert any to be able to run it with .NET Core
public static string RenderViewToString(this Controller controller, string ...
- 23.9k
115
votes
15
answers
104k
views
Configuration.GetSection always returns Value property null
Every time I call Configuration.GetSection, the Value property of the returned object is always null.
My Startup constructor
public Startup(IHostingEnvironment env)
{
var builder = new ...
- 1,410
114
votes
7
answers
101k
views
How to fix "The CORS protocol does not allow specifying a wildcard (any) origin and credentials at the same time" error
I've already enabled CORS on the project in C# .net Core
In startup.cs I've added lines
...
services.AddCors();
...
app.UseCors(builder => builder
.AllowAnyOrigin()
.AllowAnyMethod()
...
- 3,274
113
votes
16
answers
198k
views
The configuration file 'appsettings.json' was not found and is not optional
The Azure error is:
.Net Core: Application startup exception:
System.IO.FileNotFoundException: The configuration file
'appsettings.json' was not found and is not optional.
So this is a bit ...
- 1,341
113
votes
7
answers
110k
views
Startup.cs in a self-hosted .NET Core Console Application
I have a self-hosted .NET Core Console Application.
The web shows examples for ASP.NET Core but I do not have a web server. Just a simple command line application.
Is it possible to do something like ...
- 9,679
112
votes
32
answers
88k
views
Project file is incomplete. Expected imports are missing
After format my computer I reinstalled Vs 2017 V 15.6.3
and install ASP.Net Core SDK from Microsoft 2.1.4
But when I create new asp core application VS failed with error
"Project file is ...
- 1,331
112
votes
1
answer
40k
views
How to override ASP.NET Core configuration array settings using environment variables
TL;DR
In an ASP.NET Core app, I have an appsettings.json config file which uses a JSON array to configure a collection of settings.
How do I override a setting of one of the array objects using ...
- 5,151
111
votes
6
answers
80k
views
.Net Core 2.0 Process.Start throws "The specified executable is not a valid application for this OS platform"
I need to let a .reg file and a .msi file execute automatically using whatever executables these two file types associated with on user's Windows.
.NET Core 2.0 Process.Start(string fileName) docs ...
- 1,359
111
votes
7
answers
79k
views
Populate IConfiguration for unit tests
.NET Core configuration allows so many options to add values (environment variables, json files, command line args).
I just can't figure out and find an answer how to populate it via code.
I am ...
- 8,265
110
votes
19
answers
178k
views
The current .NET SDK does not support targeting .NET Core 2.1. Either target .NET Core 2.0 or lower, or use a .NET SDK that supports .NET Core 2.1
have tried upgrading to the professional version of visual studio 2017 v 15.6.0 (Preview 7.0)
and installed aspnetcore-runtime-2.1.0-preview1-final-win-x64 and .net core SDK 2.1.4.
When I created a ...
- 1,292
109
votes
8
answers
99k
views
No service for type 'Microsoft.AspNetCore.Identity.UserManager`1[Microsoft.AspNetCore.Identity.IdentityUser]' has been registered
What is the possible cause of this error:
InvalidOperationException: No service for type 'Microsoft.AspNetCore.Identity.UserManager [Microsoft.AspNetCore.Identity.IdentityUser]' has been registered....
- 1,423
108
votes
4
answers
68k
views
How do you multi-target a .NET Core class library with csproj?
When .NET Core still used the project.json format, you could build a class library targeting multiple frameworks (e.g. net451, netcoreapp1.0).
Now that the official project format is csproj using ...
- 28.8k
108
votes
5
answers
148k
views
Command line to install/upgrade .NET Core
Are there command line commands to install or upgrade .NET Core?
I checked to see if I had .NET Core was installed on my computer using dotnet --version only to notice that I still had the preview ...
- 28.4k