Error C2228 left of '.size' must have class/struct/union on Winform - string

Question

I'm creating my first program on Winform with C++. I have a function and a string input. However, when I run the program, I get the following error with text.size(): "Error C2228 left of '.size' must have class/struct/union"
Relevant code:
private: System::Void bntGet_Click(System::Object^ sender, System::EventArgs^ e) {
in_itext = txtText->Text;
itext = Convert::ToString(in_itext);
for (Int32 index = 1; index <= itext.size(); index++)
{
if (itext[index] == '#')
{
while (itext[index - 1] != ' ')
{
index--;
}
while (itext[index] != ' ')
{
next_email += itext[index];
index++;
if (itext[index] == '\0')
break;
}
break;
}
}
txtEmail->Text = next_email;
}
Any suggestions? Thanks everyone!

Answer 1

Standard warning: While it's certainly possible to write the main body of your application in C++/CLI, or even write the GUI in C++/CLI using WinForms, it is not recommended. C++/CLI is intended for interop scenarios: where C# or other .Net code needs to interface with unmanaged C++, C++/CLI can provide the translation between the two. For primary development, it is recommended to use C# with either WinForms or WPF if you want managed code, or C++ with MFC if you want unmanaged.
That said:
for (Int32 index = 1; index <= itext.size(); index++)
and
"Error C2039 'length': is not a member of 'System::String'"
Size is not how you get the length of a System::String in .Net. For that, you want the Length property. You were close on your second attempt, but you need a capital "L". (size() is how std::string does it, but std::string is a completely different beast from System::String.)
Other issues:
in_itext = txtText->Text;
itext = Convert::ToString(in_itext);
It's already a string, you don't need to convert it.
while (itext[index - 1] != ' ')
{
index--;
}
You can easily run off the beginning of the string if you do this. (You'll get an exception when index is equal to zero.) Add a check against zero.
while (itext[index] != ' ')
{
next_email += itext[index];
index++;
if (itext[index] == '\0')
break;
}
Strings in .Net are not null-terminated, you need to check against the Length.
If we take a step back, what problem are you actually trying to solve here? My best guess is that you've got some text with an email address somewhere in the middle, and you just want to extract the email address. If that's the case, then I'd probably try using a regular expression to extract the email address. You've got the full power of the .Net Library available to you, use it! See Using a regular expression to validate an email address for the regex to use, and read up on regular expressions with the introduction page and class reference.