I've build a large program with many references. F.e.:
System.Data.DataSetExtensions
System.Linq.Dynamic
I've to write a Dynamic Linq Expression:
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx
In my case:
Dim query As IEnumerable = ds.Sales.Where(strWhere)
But with System.Data.DataSetExtensions Where is misinterpreted. The compiler expects (Datarow, Integer, Boolean). If I delete System.Data.DataSetExtensions everything is ok with this expression, but I get many other errors, so I need this reference.
What can I do that the Where is interpreted correctly?
Is the large programm all in one file?
If not done already, split up your program into classes, then put each class into it's own file. Then only use the required references in every file.
Maybe this way you will be able to resolve the namespace conflict.
If for some reason you absolutely need both conflicting namespaces and can't resolve the ambiguity, you can directly call the extension method. Basically the extension method is just another static method on another class. ds.Sales.Where(strWhere) is only syntactic sugar for that method call.
An example:
ds.Sales.AsEnumerable().Where(yourCondition)
Would translate to
EnumerableRowCollectionExtensions.Where(ds.Sales.AsEnumerable(), yourCondition)
Related
this is the Interface:
Namespace IBasBS100
Public Interface IBasBSMoedas <DispId(0)> <Obsolete("This method is obsolete. Use Actualiza(BasBE100.BasBEMoeda objMoeda, ref string strAvisos) instead.", False)>
Sub Actualiza(objMoeda As BasBEMoeda, Optional strAvisos As String = "")
<DispId(18)>
Sub Actualiza(objMoeda As BasBEMoeda, ByRef strAvisos As String)
<DispId(2)>
when i try to call the function that is not depracated it gives me the ambiguous error message:
Dim avisos As String
Dim bsmoedas As IBasBSMoedas = MotorPRI.Base.Moedas
bsmoedas.Actualiza(m, avisos)
I think its calling the depracated method.
Is there any way that i could explicitly call the non depracated method "Actualiza(objMoeda As BasBEMoeda, ByRef strAvisos As String)"?
PS: I can not change the interface, it's an external Library
I can only assume that the interface code was written in C# because that VB code won't compile. In VB, you don't explicitly state when passing an argument by reference, so the there's no way to differentiate between those two methods when calling one in VB code. In C#, you specify the ref or out keyword when passing an argument by reference, so there is no ambiguity in which overload you are calling, so it's allowed.
In short, you cannot call that interface method in VB. You can implement the interface in a class in VB and use a different name for one of the methods but you'd still have to call it through the class, not the interface. If you want to be able to use that interface then you're going to have to do it in C# code. Perhaps write a library in C# for the code that uses that interface and then consume that in your VB app.
I guess the other alternative to do it in VB would be to do so via Reflection. Far from ideal but I don't see another way.
Primavera v10 funtions and VisualBasic aren't compatible with each other. Some may work, most won't. I would recommend changing to C# since this is the "supported" language of primavera.
Does anyone know how to put the enableCors into the controller on vb.net. i am working along with a pluralsight course and tried a code translator with no luck. my attempt is below.
<EnableCors(origins: "http://localhost:53080", headers: "*", methods: "*")>
The correct syntax would be something like this:
<EnableCors("http://localhost:53080", "*","*")>
The C# example appears to use named parameters. VB.NET supports that too, however the EnableCorsAttributes has properties and contractor arguments that only differ by letter casing. This confuses the compiler as to whether you are attempting to set the named parameter or the property in the attribute. So, in this case we can just drop the named arguments all together.
In Vb.net this <EnableCors("http://localhost:53080", "*","*")> will work, but, you have to add on NuGet the Microsoft.AspNet.WebApi.Cors and Microsoft.AspNet.Cors. You need to add Imports System.Web.Http.Cors on the class.
Remove any empty line between the http://localhost:53080", "*","*")> and the declaration of the controller class.
I have some code like this:
MyClass::MyClass(MyClass^ objToCopyFrom);
Which is producing an error:
'type' : ref class does not have a user-defined copy constructor
When I look up the error, it suggests my code should look like this:
MyClass::MyClass(MyClass% objToCopyFrom);
My question is therefore, which version is correct or are they both correct?
Only your second version is correct:
MyClass::MyClass(MyClass% objToCopyFrom);
or its variant:
MyClass::MyClass(const MyClass% objToCopyFrom);
MyClass% is a so-called Tracking Reference which is the conceptual equivalence of a reference in native C++, only for CLR types.
While copy constructors in native C++ can have a number of different signatures, what they all have in common is that the other object that's being copied is passed in as a reference. C++/CLI stays close to that principle, but uses its own type of object references, a tracking reference.
I am currently writing a wrapper for a native C++ class in CLI/C++. I am on a little GamePacket class at the moment. Consider the following class:
public ref class GamePacket
{
public:
GamePacket();
~GamePacket();
generic<typename T>
where T : System::ValueType
void Write(T value)
{
this->bw->Write(value);
}
};
I want that I'm able to call the function as following in C#, using my Wrapper:
Packet.Write<Int32>(1234);
Packet.Write<byte>(1);
However, I can't compile my wrapper. Error:
Error 1 error C2664: 'void System::IO::BinaryWriter::Write(System::String ^)' : cannot convert argument 1 from 'T' to 'bool'
I don't understand this error, where does the System::String^ comes from. I'm seeing a lot of overloads of the Write() method, does CLI/C++ not call the correct one, and if so, how can I make it call the correct one?
Reference MSDN: http://msdn.microsoft.com/en-us/library/system.io.binarywriter.write(v=vs.110).aspx
Templates and generics don't work the same.
With templates, the code gets recompiled for each set of parameters, and the results can be pretty different (different local variable types, different function overloads selected). Specialization makes this really powerful.
With generics, the code only gets compiled once, and the overload resolution is done without actually knowing the final parameters. So when you call Write(value), the only things the compiler knows is that
value can be converted to Object^, because everything can
value derives from ValueType, because your constraint tells it
Unfortunately, using just that information, the compiler can't find an overload of Write that can be used.
It seems like you expected it to use Write(bool) when T is bool, Write(int) when T is int, and so on. Templates would work like that. Generics don't.
Your options are:
a dozen different copies of your method, each of which has a fixed argument type that can be used to select the right overload of BinaryWrite::Write
find the overload yourself using reflection, make a delegate matching the right overload, and call it
use expression trees or the dynamic language runtime to find and make a delegate matching the right overload, and then you call it
In my language I can use a class variable in my method when the definition appears below the method. It can also call methods below my method and etc. There are no 'headers'. Take this C# example.
class A
{
public void callMethods() { print(); B b; b.notYetSeen();
public void print() { Console.Write("v = {0}", v); }
int v=9;
}
class B
{
public void notYetSeen() { Console.Write("notYetSeen()\n"); }
}
How should I compile that? what i was thinking is:
pass1: convert everything to an AST
pass2: go through all classes and build a list of define classes/variable/etc
pass3: go through code and check if there's any errors such as undefined variable, wrong use etc and create my output
But it seems like for this to work I have to do pass 1 and 2 for ALL files before doing pass3. Also it feels like a lot of work to do until I find a syntax error (other than the obvious that can be done at parse time such as forgetting to close a brace or writing 0xLETTERS instead of a hex value). My gut says there is some other way.
Note: I am using bison/flex to generate my compiler.
My understanding of languages that handle forward references is that they typically just use the first pass to build a list of valid names. Something along the lines of just putting an entry in a table (without filling out the definition) so you have something to point to later when you do your real pass to generate the definitions.
If you try to actually build full definitions as you go, you would end up having to rescan repatedly, each time saving any references to undefined things until the next pass. Even that would fail if there are circular references.
I would go through on pass one and collect all of your class/method/field names and types, ignoring the method bodies. Then in pass two check the method bodies only.
I don't know that there can be any other way than traversing all the files in the source.
I think that you can get it down to two passes - on the first pass, build the AST and whenever you find a variable name, add it to a list that contains that blocks' symbols (it would probably be useful to add that list to the corresponding scope in the tree). Step two is to linearly traverse the tree and make sure that each symbol used references a symbol in that scope or a scope above it.
My description is oversimplified but the basic answer is -- lookahead requires at least two passes.
The usual approach is to save B as "unknown". It's probably some kind of type (because of the place where you encountered it). So you can just reserve the memory (a pointer) for it even though you have no idea what it really is.
For the method call, you can't do much. In a dynamic language, you'd just save the name of the method somewhere and check whether it exists at runtime. In a static language, you can save it in under "unknown methods" somewhere in your compiler along with the unknown type B. Since method calls eventually translate to a memory address, you can again reserve the memory.
Then, when you encounter B and the method, you can clear up your unknowns. Since you know a bit about them, you can say whether they behave like they should or if the first usage is now a syntax error.
So you don't have to read all files twice but it surely makes things more simple.
Alternatively, you can generate these header files as you encounter the sources and save them somewhere where you can find them again. This way, you can speed up the compilation (since you won't have to consider unchanged files in the next compilation run).
Lastly, if you write a new language, you shouldn't use bison and flex anymore. There are much better tools by now. ANTLR, for example, can produce a parser that can recover after an error, so you can still parse the whole file. Or check this Wikipedia article for more options.