string.EndsWith works differently? What am I missing?

[wstaelens]

In real life I have an asp.net core web application with Blazor server components running .net 7 (windows) (A).

Calls are made to another class library (.net 7 windows) (B) which in turn makes calls to a class library (.net framework 4.8) (C).

(A) --> (B) --> (C)

string is being passed down the road. Finally B makes a call to a static method in C passing a parameter string bar.

In the static method of library C a check happens if it is not a null-terminated string, add '\0' (or "\0")

   // method in class library C
   public static void Foo(string bar)
  {
     if (!bar.EndsWith("\0"))
     {
        bar += "\0";
     } else {

     }
  } 

when I pass in the string "abc" making the call from B (.net 7) to C (.net framework 4.8) the bar += "\0"; does not happen.

when I pass the string "abc" making the call from B (.net framwork 4.8) to C (.net framework 4.8) the bar += "\0"; happens.

Library C makes calls to e.g. XcvData which requires a null-terminated string. Code was failing on different locations while it turned out that trivial code string.EndsWidth didn't work.

(Checked with .EndsWith(char.MinValue.ToString()) ) and char c = bar.Last())

In Visual Studio 2022 17.7.5 Pro x64 when I hover the parameter string bar I see "abc" as value of type string.
(.net 7.0.402 sdk - windows 10 22h2 19045.3633)

How is this string being passed/marshalled. When switching from .net 6 to .net 7 we started having exceptions, so I think something changed to strings or marshalling of strings?

What am I missing here? Why does this happen?

--> How do I properly check if string ends with '\0' when call from B (.net 7) to C (.net framwork 4.8) is made?

attached sample solution (.zip file) ConsoleApp1.zip

[huoyaoyuan]

#92025 (comment)

You can use StringComparison.Ordinal to change the behavior.

[wstaelens]

OMG