Writing to forms label

[coldneut]

I am new to VC++ but have used Borland C++ Builder for many years.

I am trying to write to a forms label using

char s{40];
strcpy(s,"Hello World");
Label1->Text = s;

I get

cannot convert from 'char *' to 'System::String ^'

Can someone give me an example of how to do this?

[Alex F]

Label1->Text = "Hello, World";
or
Label1->Text = L"Hello, World";

One of these versions will be OK.
BTW, why do you work with CLR project? Is this really what you need?

[coldneut]

Label1->Text = "Hello, World";
or
Label1->Text = L"Hello, World";

These work but I need to change the text periodically and am trying to do this with a changeable character array.

e.g.
char s[40];
float a = 123.45;
sprintf(s,"%.2f",a);
Label1->Text = s;

This is where I get -
cannot convert from 'char *' to 'System::String ^'

I am working with a CLR project because when I created a forms project it told me it was converting my project to CLR. I don't even know what CLR is or does.

[krmed]

Not sure if this will solve your problem, but instead of

char s[40];
float a = 123.45;
sprintf(s,"%.2f",a);
Label1->Text = s;

try using this

TCHAR s[40];
float a = 123.45;
_stprintf_s(s,_T("%.2f"), 40, a);
Label1->Text = s;

Hope that helps.

[Alex F]

You are writing mixed managed-unmanaged code without any need.
C++/CLR requires good knowledge of both native C++ and .NET. According to your needs, you may decide to go to pure native solution, with using MFC or WTL as UI Framework, or pure .NET solution using C#.
C++/CLI is used only in rare cases, for managed-unmanaged interoperability.
For your specific problem, tale a look at .NET String class and String.Format function, which replaces native sprintf.

[coldneut]

I tried your suggestion and get:

1>c:\orbitalprogram\orbital\orbital\Form1.h(189) : error C2664: 'void System::Windows::Forms::Control::Text::set(System::String ^)' : cannot convert parameter 1 from 'TCHAR [40]' to 'System::String ^'
1> Reason: cannot convert from 'TCHAR *' to 'System::String ^'
1> No user-defined-conversion operator available, or
1> Cannot convert an unmanaged type to a managed type

on the statement:
Label1->Text = s;

[coldneut]

I tried to go to MFC and various other options to build a project using Windows Forms. I really need Windows Forms but when I select it, I get the message it is converting to CLR.

The only problem I have with the CLR approach is the problem of setting
Label1->Text = s; where s is a character array defined by char s[40];

I really need to do this.

[Alex F]

I suggested you to use String::Format function. Did you try this?

[coldneut]

I've tried many combinations of String:Format with no success. I just don't know how to use it.
Could you please give me the missing puzzle piece so I can get on track.

I need:

double V = 1.2345;
char s[40];
String^ StrVal;
sprintf(s,"%.4f",V);

(Set Strval string to s contents)

Label1->Text = StrVal;

[Alex F]

I wonder why you write sprintf and call this String.Format.
http://msdn.microsoft.com/en-us/libr...ng.format.aspx

[coldneut]

double V = 1.2345;
String^ StrVal;
StrVal = String::Format("F01", V);
Label1->Text = StrVal;

I get F01 displayed instead of 1.2

[Alex F]

Do you really read something before asking the question?

StrVal = String::Format("{0}", V);
StrVal = String::Format("{0,8:0.000}", V);
StrVal = String::Format("{0:0000.000}", V);

[coldneut]

Alex,

That worked. Many thnanks for your patience. I have spent a lot of time trying to find this information to no avail.

[TheGreatCthulhu]

I'd just like to add that a simpler way would be to declare a .NET string:

// this declares a variable of a reference type (a.k.a __gc type) string,
// also known as a pointer to an object on the managed heap,
// or a handle to a managed object. The ^ replaces __gc* sintax.
String^ s;

This can be initialized in the constructor, and its value can be manipulated anytime by simply assigning a new string

s = "some text";

or by using the ToString() method which all .NET types inherit from System::Object

double d = 1.2345;
s = d.ToString();

P.S. I think that, when you create a .NET (CLR) project, all the fundamental type keywords should be aliases of their .NET equivalents.