System.IO.FileNotFoundException

The exception that is thrown when an attempt to access a file that does not exist on disk fails.

Minimum version: >= 1.1 >= Core 2.0

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How to handle it

try
{

}
catch (System.IO.FileNotFoundException e)
{

}
try
{

}
catch (System.IO.FileNotFoundException e) when (e.Message.Contains("something"))
{

}
try
{

}
catch (System.IO.FileNotFoundException e) when (LogException(e))
{

}

private static bool LogException(Exception e)
{
    logger.LogError(...);
    return false;
}

How to avoid it

Before
try
{
    File.ReadAllText("non-existing.file");
}
catch (FileNotFoundException e)
{
    Console.WriteLine(e.ToString());
}
After
if (File.Exists("non-existing.file"))
{
    File.ReadAllText("non-existing.file");
}

Links

YouTube videos

Possible fixes from StackOverflow

Believe it or not, this is normal behaviour. An exception is thrown but handled by the XmlSerializer, so if you just ignore it everything should continue on fine.

I have found this very annoying, and there have been many complaints about this if you search around a bit, but from what I've read Microsoft don't plan on doing anything about it.

You can avoid getting Exception popups all the time while debugging if you switch off first chance exceptions for that specific exception. In Visual Studio, go to Debug -> Exceptions (or press Ctrl + Alt + E), Common Language Runtime Exceptions -> System.IO -> System.IO.FileNotFoundException.

You can find information about another way around it in the blog post C# XmlSerializer FileNotFound exception (which discusses Chris Sells' tool XmlSerializerPreCompiler).

I believe I had the same issue as you did. I didn't save the whole error message, but my error message was

'Could not load file or assembly 'Microsoft.Build.Framework, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.'

I am using Visual Studio 2017 and was trying to do Update-Database after Add-Migration.

To resolve the issue I closed Visual Studio and re-opened it, then re-ran Update-Database again.

This may or may not resolve your issue, but I thought I'd post just in case it would help.

Our local build script was using an older version of nuget.exe (4.7.1.5393) to restore NuGet packages. We started getting this error after updating to Visual Studio 2019 version 16.5.0. Updating to the latest version of nuget.exe (5.4.0.6315) fixed the issue for us.

nuget.exe can be downloaded here: https://www.nuget.org/downloads.

In My case the file appsettings.json existed in project folder, but it was set to Do not copy, I changed the setting to Copy always (see images below). And it worked for me.

It will automatically added following XML to your project.csproj file:

<ItemGroup>
    <Content Update="appsettings.json">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </Content>
</ItemGroup>

I have looked at other answer, project.json is dead as this answer says.

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I've found a workaround that seems to resolve the issue for good, at least on my environment running VS 2017 Professional 15.5.2 and Entity Framework 6.1.1.

Basically, install the DLL (with a few related ones) into the GAC (Global Assembly Cache) and the issue will go away.

Follow these steps:

  1. Close all running instances of Visual Studio 2017

  2. Launch the Visual Studio 2017 Developer Command Prompt

  3. Type the following commands (replace Professional with your edition, either Enterprise or Community, or adjust the path accordingly):

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.Framework.dll"

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.dll"

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.Engine.dll"

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.Conversion.Core.dll"

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.Tasks.Core.dll"

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.Build.Utilities.Core.dll"
  1. Restart Visual Studio 2017

In essence, the GAC will (in most cases) be given priority when .NET is trying to load a DLL and the FileNotFoundException will go away as your DLL will now be resolved through the GAC.

Again, it works for me and it's simply a workaround, it won't solve the core issue itself but at least I don't have to restart VS all the time when trying to work with EF migrations, and that's good enough for me.