Call MSBuild passing it a single task to run - msbuild

Question

We can define a target in a csproj file and then specify that target when we call msbuild from the command line. That looks like this:
my.csproj
<Target Name="CopyFiles">
<Copy
SourceFiles="#(MySourceFiles)"
DestinationFolder="c:\MyProject\Destination" />
</Target>
msbuild
msbuild my.csproj /t:CopyFiles
The CopyFiles targets asks msbuild to run the Copy task.
What if we don't want to edit the csproj file. How can we define a target just from the command line? Alternatively, using only the command line, how can we ask msbuild to run just one or maybe two tasks?
Pseudo-Code
msbuild my.csproj /t:"Copy SourceFiles=#(MySourceFiles) DestinationFolder=..."

Answer 1

Based on the MSBuild Command-Line Reference, this isn't possible exactly as you describe it, i.e. MSBuild will not take Target definitions from the command-line input. They have to be defined in a file somewhere.
But, you can have a script (maybe even a .bat?) that does something like:
Create a new, essentially empty, project file.
Import the .csproj, with <Import Project="foo.csproj" />
Add the targets
Call MSBuild with the new project file with the targets you want. Multiple targets can be specified by multiple /t: switches. Properties can be specified with /p:
The final, programmatically/script generated project file might look something like:
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Import Project="foo.csproj" />
<Target Name="CopyFiles">
<Copy
SourceFiles="#(MySourceFiles)"
DestinationFolder="$(Destination)" />
</Target>
</Project>
The actual MSBuild command called might then be:
msbuild temp.proj /t:CopyFiles /p:"Destination=c:\MyProject\Destination"