Resolve error MSB4126: The specified solution configuration "Debug|x64" is invalid

Issue context

Create a .NET solution with .NET CLI:

dotnet new sln

When building with dotnet build command, you may encounter the following error:

error MSB4126: The specified solution configuration "Debug|x64" is invalid

You may also encounter similar errors if you CPU is different from x64.

There are at least two approaches to address this issue.

Remove Platform environment variable

This issue usually occurs because there is one environment variable named Platform or platform with value as x64. You can remove if from your system environment variables or session environment variables.

Add x64 platform configuration

Another approach is to add one configuration for x64 directly in your solution.

Here are the steps to resolve this issue:

• Open your solution file (.sln) in a text editor.

• Look for the GlobalSection(SolutionConfigurationPlatforms) section.

• Under this section, ensure that there is an entry for Debug|x64. If not, add it. The section should look something like this:

GlobalSection(SolutionConfigurationPlatforms) = preSolution
    Debug\|x64 = Debug\|x64
    Release\|x64 = Release\|x64
EndGlobalSection

• Save the solution file and try to build again.