I am trying to learn f# and copy some sample from internet. When copy to visual studio, it shows me a lot of red line as show in the following picture.
Some of your objects (like XName or XElement) are belonging to classes defined in the assembly System.Xml.Linq.dll.
The line open System.Xml.Linq is the C# equivalent line using System.Xml.Linq; that allows you to use the methods defined in the referenced assembly in your code.
If the assembly is not referenced (you didn't add the reference to System.Xml.Linq to the project), you have that error.
Remember that you can reference (as #Petr said), if you're using F# script files or F# interative, the assemblies you want using: #r "AssemblyNameHere". Other info about scripting and this option in this blog post.
Hover mouse over the red squiggles and a tooltip will popup. That tooltip explains what assembly you should reference.
Related
I'm writing a simple F# console app with Visual Studio 2017 targeting .NET Core 2.0. I'm wondering if it's possible to open a module not present in the current directory.
For example :
/root/foo.fs
/root/SubDirectory/bar.fs
How can bar.fs open the Foo module or vice versa?
I already tried :
open Foo
open "../Foo"
open "C:/AbsolutePath/Foo"
With the last two ones, VS complained with :
FS0010 : Unexpected string literal in open declaration. Expected identifier, 'global' or other token.
There seems to be no documentation about this.
Any help would be appreciated.
Actually you can only add or reorder files in VS2017 in the preview version I believe (so not yet on 15.5.6). But TheQuickBrownFox is correct, the file that has your module has to be in the fsproj file, and the order is important.
For VSCode, you can use the Command (or Project Explorer) in Ionide: Ctrl+Shift+P: F#: Add Current File to Project and also F#: Move File Up/Down (there's a right click meny on the F# Project Explorer as well.
In Visual Studio 2017 you can right-click the Project and choose Edit .fsproj. VS will reload the file automatically on save, so no need to unload a project like in VS2015. It will look something like this:
You can see that MyModule.fs is in the root of the project and the line with MyModule.fs needs to be above any other files that reference it. You can use Alt+Up/Down Arrow to move lines around.
Then you can just open this module and use it. For example Add is defined in this module.
I also added the #load directive, this is only if you want to test it in FSI, and the compiler will ignore it.
Is there a way within FSI that I can reference and use registered COM components?
In a normal .fs compiled program I can simply reference the component in question and then open the relevant generated namespace(s). In a .fsx file, however, I can't seem to replicate this behaviour. I have tried using #r to reference the .dll directly, and I have tried using #I to point to the directory followed #r both with the library's "friendly" name and the file name, but nothing seems to work.
Are you only able to reference .NET assemblies from a .fsx? I don't really want to have to write/gen a wrapper assembly. I am hoping there might be a way to force FSI to take whatever steps the normal executable takes in order to provide the interop layer.
When you add a reference to a COM component in Visual Studio, it invokes a tool to generate a wrapper (standard .NET assembly) and then references the wrapper.
If you want to reference COM from fsx, you'll need to generate the wrapper yourself (or find the one generated by Visual Studio?) The tool that generates the wrapper that is called TlbImp.exe (see Type Library Importer on MSDN).
I have a 3rd party .dll that I have successfully added as a reference in both a VS 2010 C# project and an F# VS 2010 project. I can view the contents in the object browser in both cases, but the F# version won't let me "open" the library. It works fine in the C# project (with the "using" directive), and I can write a program that uses the contents of this particular .dll. I have not had any trouble with other .dlls in F#/VS 2010/.NET 4.0 on Windows 7.
Any ideas as to why this might be happening? Or how I could debug this further?
See what the csc.exe and fsc.exe command-lines have for the library in question (in VS, open the 'Output Window' after a rebuild), to see if they both have the same reference (e.g. -r:Path\Library.dll).
And to be clear, you're saying
open NagLibrary
in F# yields the error message in the title, but
using NagLibrary;
in C# works and opens the namespace?
make sure you reference the path within the script using the double "\" convention
for me this worked
#r "C:\homeware\\blp\\api\\APIv3\\DotnetAPI\\v3.4.5.4\\lib\\Bloomberglp.Blpapi.dll"
open Bloomberglp.Blpapi
I would like to use the F# interactive console with the projects in the currently open solution in Visual Studio 2010. Is there a quick and easy way to add a reference in the F# interactive console to reference projects in the currently open solution?
I've got lines like this at the top of my .fs file:
#if INTERACTIVE
#r #"C:\path\to\some.dll"
#I #"C:\Users\bford\path\to\a\project\in\this\solution\bin\Debug"
#r "Project.name"
#endif
Alt-Enter now drops me into fsi with all the required stuff loaded
If it's a project you reference often, you can add an 'always' reference to the FSI command line, under Tools->Options->F# Tools->F# interactive options.
Add a -r switch like:
-r "C:\Users\yaddayadda\MyDll.dll"
I don't think there is any direct way to reference a project in the solution. The best way I can think of is to add a FSX file somewhere to your project with the #r directive:
#r #"bin\Debug\YourProject.dll"
Then you can at least reference the compiled DLL file simply by hitting Alt+Enter in Visual Studio. As far as I know, you cannot reference the project - you can only reference an assembly.
Currently, F# Interactive is really disconnected from the project system in Visual Studio. I suppose that closer integration would be quite useful (but probably difficult to provide).
Now in Visual Studio 2013 you can add a reference to the F# interactive window by right clicking on the referenced dll and clicking "Send to F# interactive".
I would think it should be straightforward to reference the current project, obtain the list of references it contains, and then optionally generate a list of #r (and possibly #i) statements for the interactive session being created, referencing the dll of the project itself as well.
For example: "fsi /i:pathOfLib1 /r:lib1 /i:pathOfLib2 /r:lib2 ...."
PS: base on the MSDN article it doesn't appear that library names can include their path prefixes hence the separate into /i and /i : http://msdn.microsoft.com/en-us/library/dd233172%28v=vs.100%29.aspx
It would be good if the Visual Studio F# Interactive Options menu allowed for the stipulation of a startup script that the invocation could pass to FSI via the "--use:" directive. Such a script could then be passed solution metadata that allows for the environments to be more integrated such as loading latest project outputs.
I'm trying to use the Seq.generate_using function but unfortunately, I don't seem to be able to find it. I thought it would be living here:
Microsoft.FSharp.Collections.Seq.generate_using
But it doesn't. I am getting the error listed below.
C:\Users\Owner\Documents\Visual Studio
2008\Projects\fsharp1\Program.fs(54,63):
error FS0039: The value, constructor,
namespace or type 'generate_using' is
not defined. A construct with this
name was found in
FSharp.PowerPack.dll, which contains
some modules and types that were
implicitly referenced in some previous
versions of F#. You may need to add an
explicit reference to this DLL in
order to compile this code.
According to the Sept 2008 CTP Release Notes:
The F# library is split into two
components. FSharp.Core.dll: Contains
the core F# libraries, which will be
stabilized and versioned infrequently.
FSharp.PowerPack.dll: Contains
additional useful F# libraries and
tools which will version more
frequently, and allow continued
innovation on top of the core F#
language and libraries.
Some methods in the Seq module were moved into the FSharp.PowerPack assembly, so you can only get those methods by doing the following:
If you're using Visual Studio, open your Solution Explorer, right-click on the project file, choose "Add Reference", and add "FSharp.PowerPack.dll".
If you're using a script file or fsi, then type #r "FSharp.PowerPack";; to load the assembly.
Now you should be able to call Seq.generate_using.
The #r "FSharp.PowerPack";; works for me but the addition of PowerPack to my solution does not. I am trying to use HashSet<>.