Question

Or, ‘am I doing it wrong’?

I am writing a small function that will return a string, quoted (as quoted-printable) if necessary, otherwise it returns it as is. A character is input into the function; the result is a string.

What I tried to do at first was:

private string QuotedChar(char ch) {     if(ch < (char)128 && !char.IsWhiteSpace(ch))         return(new string(ch));      // ... } 

However, the compiler says CS0214, ‘Pointers and fixed size buffers may only be used in an unsafe context’, when compiling that return statement. If I change the code to say instead:

private string QuotedChar(char ch) {     if(ch < (char)128 && !char.IsWhiteSpace(ch))         return(new string(new char[] { ch }));      // ... } 

… it works just fine. However that seems rather pointless. I don’t understand why it thinks I am trying to use a pointer or a fixed size buffer, since it’s just a char. Am I missing something seriously silly, or is this a problem/bug?

FYI, this is Mono 2.0, not the Microsoft .NET Framework. I don’t run Windows, so I don’t have Microsoft’s C# compiler to see if it does the same thing or not, which is why I wonder if it is a bug.

Answer 1

Well, it’s not a bug that it doesn’t compile. There’s no string constructor overload which takes a char. I suspect that Mono thought you meant the string(char*) constructor and tried that – leading to the error.

The simplest way of converting a char to a string is simply to call ToString() though:

private string QuotedChar(char ch) {     if(ch < (char)128 && !char.IsWhiteSpace(ch))         return ch.ToString()      // ...  } 

The MS C# compiler guesses the same overload, but gives a different error message:

Test.cs(8,20): error CS1502: The best overloaded method match for 'string.String(char*)' has some invalid arguments
Test.cs(8,31): error CS1503: Argument ‘1’: cannot convert from 'char' to 'char*'