Here is the answer (of my question ... with the help of WiredPrairie, ... ;-) )
This line
<Import Project="$(VSToolsPath)\TypeScript\Microsoft.TypeScript.targets" Condition="'$(BuildingInsideVisualStudio)' == 'true'" />
was preceeding my lines
<PropertyGroup Condition="'$(Configuration)' == 'Debug'">
<TypeScriptTarget>ES5</TypeScriptTarget>
<TypeScriptRemoveComments>true</TypeScriptRemoveComments>
<TypeScriptSourceMap>true</TypeScriptSourceMap>
<TypeScriptModuleKind>AMD</TypeScriptModuleKind>
</PropertyGroup>
<PropertyGroup Condition="'$(Configuration)' == 'Release'">
<TypeScriptTarget>ES5</TypeScriptTarget>
<TypeScriptRemoveComments>true</TypeScriptRemoveComments>
<TypeScriptSourceMap>true</TypeScriptSourceMap>
<TypeScriptModuleKind>AMD</TypeScriptModuleKind>
</PropertyGroup>
So I put it AFTER ( what a smart guys, isn't it ;-) ) in my *.csproj
I found the problem because:
The //# sourceMappingURL=/path/to/file.js.map
was generated at the end of the *.js files when saving, not when compiling.
The build output was saying The TypeScript Compiler was given an empty configurations string, which is unusual and suspicious.
.
The solution comes from this post: TypeScript Compiler was given an empty configurations string.
The root cause of the problem appears when I tried to deploy my project to Azure. The js files were not uploaded/compiled, so i've added this tricky line in the csproj bad luck :-(
Thank and I hope it will help others.