I'm making a batch development kit in visual basic and i need to be able to call a function that sets textboxes to a saved files text. How do i do this without returning? I tried this, and it lets me run the program, but gives me a warning, not an error. How do i go about doing this? Here is my little function design. P.S. I recently switched back to VB from Java and i'm so used to doing public void. Thanks in advance!
Public Function loadProject()
End Function
You want a Sub, which is the equivalent to the Java void method.
Public Sub LoadProject()
End Sub
It's not a bad Idea to just have a function that returns a value like a success statement just in case you need it. A call to the function doesn't have to accept or use the return value from the function.
You could even build a class with two values - txtpreviousvalue and txtnewvalue
Have your function return that type and fill an instance of the type with the respective values.
One day, if you need it, you'll have it.
P.S. I'm only posting this as an answer because the good answer posted by sstan is not marked as the answer; You should probably do that.
Related
I like to try to optimize my code, and I would like to measure the time taken by a function.
I have a class named Chrono. So I just have to add chrono.start at the beginning of the function, and chrono.stop at the end. My class chan also add the times it measure in a list, to then have average time, total time...
It works. Only problem is when there is exit sub or return in the middle of the function. Not really a problem, I just add a Try at the begginf of the function, and put my chrono.stop in the finally portion. I'm not sure it's really efficient, but it works.
So here is my question : I would like to have a function taking function name as parameter, that will automatically launch and stop my class when this function is called. I have heard of Reflection, but I have no idea how to use it. And it's really hard to search for this question in the internet (because the words are too common : "do something at the end of a function")
To resume, my code works, no problem. It's just constraining to add code to a function for just a short period of time (and sometimes forgot to remove it).
Thx (I'm french and hope I'm understandable)
This is how you can use reflection to call a method by name:
using System.Reflection;
public int InvokeMethod(string name)
{
int time1 = 1; //call your chrono.start here.
Type thisType = this.GetType();
MethodInfo theMethod = thisType.GetMethod(name);
theMethod.Invoke(this, new object[] { 1 });
int time2 = 10; //call your chrono.end here.
return time2 - time1;
}
However, there is a problem. How will you know what parameters to pass to the function? In the code above, I'm passing the integer 1 (new object[] { 1 }) just for example. So this code cannot be automated, but if you run it manually against each function one by one, then you can change that line to pass the correct arguments and make it work without having to modify your function.
This is to answer your question as how to call a function by name using reflection. However, it is much easier to call it using a delegate (or Fuc<T, tRsult> in .Net v3.5 and higher).
In RealBasic (now Xojo), which I'm leaving to the past, I used to be able to declare a method like this:
Sub MyCoolSub(param1 as string, Assigns parameter2 as integer)
Do
'Waste CPU time scrying the universe.
Loop
End Sub
And then call it in this way:
MyCoolSub("Answer")=42
Now I'd want to replicate this behaviour in VB.Net.
The closest thing I stumbled upon is the Property's clauses, but VS does not let me add parameters to it that would however require some overhead which decreases the convenience of this type of declaration.
Do you have any better suggestion?
PS. As a side question I would be pretty happy to know that there is a way to comment with "//" in VB.Net, as I'm not that comfortable with the apostrophe character. Is there any thing as a VS comment characters list? Maybe an extension could do it...
When I look at the documentation for the Xojo Assigns keyword the closest thing I can think of is to create a write-only property like this:
Public WriteOnly Property theVolume(a As Integer, b As Integer) As Integer
Set(c As Integer)
Debug.WriteLine("a={0}, b={1}, c={2}", a, b, c)
End Set
End Property
theVolume(1, 2) = 3
a=1, b=2, c=3
Regarding your "P.S." note:
to ease your switching to VB.NET you can use the following AutoHotKey command:
:O://::'
This will do the appropriate substitution for you during typing.
You can limit it only to your IDE window using #IfWinActive directive.
Anyway, Roslyn VB.Net compiler is now open source so you can download and play...
In my project (which I inherited from someone) there are a lot of functions like:
Public Function DoSomething(ByVal s As String)
' Do something to public properties
End Function
And they are called like this:
DoSomething(s)
So the return value is ignored (which is object, as I see in the docs). Is it safe to change all these functions to Subs? Could I break something which isn't so obvious?
Should be safe. That's what Subs are for, this is really bad style by your predecessor.
Is there any specific reason you want to convert to Subs? From your code the Function has no return type - in this situation I can't see there being any problem.
I have a following code which works fine
MsgBox(AddSomething(Of String)("Hello", "World"))
Public Function AddSomething(Of T)(ByVal FirstValue As T, ByVal SecondValue As T) As String
Return FirstValue.ToString + SecondValue.ToString
End Function
Now we are redesigning the application to work with parameters of different types which will be provided through XML
<SomeValues>
<Add Param1="Somedata" Param2="SomeData" MyType="String"/>
<Add Param1="Somedata" Param2="SomeData" MyType="MyBusinessObject"/>
</SomeValues>
If I try to provide the following it gives error as Of accepts only type
''''Get DetailsFromXml --- MyType,Param1,Param2
MsgBox(AddSomething(Of Type.GetType(MyType))(Param1,Param2))
How to solve this issue.
Edit
The above example is given to make the question simple. Actual issue is as follows
I am using SCSF of P&P.
Following is per view code which has to be written for each view
Private Sub tsStudentTableMenuClick()
Dim _StudentTableListView As StudentListView
_StudentTableListView = ShowViewInWorkspace(Of StudentListView)("StudentTable List", WorkspaceNames.RightWorkspace)
_StudentTableListView.Show()
End Sub
Now I want to show the views dynamically.
Public Sub ShowModalView(ByVal ViewName As String)
Dim _MasterListView As >>>EmployeeListView<<<<
_MasterListView = ShowViewInWorkspace(Of >>>EmployeeListView<<<)("Employee List", WorkspaceNames.RightWorkspace)
_MasterListView.Show()
End Sub
So the part shown using the arrows above has to be somehow dynamically provided.
The point of generics is to provide extra information at compile-time. You've only got that information at execution-time.
As you're using VB, you may be able to get away with turning Option Strict off to achieve late binding. I don't know whether you can turn it off for just a small piece of code - that would be the ideal, really.
Otherwise, and if you really can't get the information at compile-time, you'll need to call it with reflection - fetch the generic "blueprint" of the method, call MethodInfo.MakeGenericMethod and then invoke it.
I assume that the real method is somewhat more complicated? After all, you can call ToString() on anything...
(It's possible that with .NET 4.0 you'll have more options. You could certainly use dynamic in C# 4.0, and I believe that VB10 will provide the same sort of functionality.)
In .Net generics, you must be able to resolve to a specific type at compile time, so that it can generate appropriate code. Any time you're using reflection, you're resolving the type at run time.
In this case, you're always just calling the .ToString() method. If that's really all your code does, you could just change the parameter type to Object rather than use a generic method. If it's a little more complicated, you could also try requiring your parameters to implement some common interface that you will define.
If all you are doing is ToString, then making the parameters object instead would solve the problem in the simplest way. Otherwise you are going to have to bind the type at run-time, which in C# looks like:
System.Reflection.MethodInfo mi = GetType().GetMethod("AddSomething");
mi = mi.MakeGenericMethod(Type.GetType(MyType));
object result = mi.Invoke(this, new object[] { Param1, Param2 });
Because it involves reflection it won't be fast though... but I assume that's not a problem in this context.
I'm calling a function that returns a string, but it's only actually returning the first character of the string it's supposed to be returning.
Here's a sample piece of code to recreate the issue I'm experiencing:
Public Function GetSomeStringValue(Value as Integer) As String
... Code Goes here
Return Some_Multicharacter_string
End Function
The function call looks like:
SomeStringValue = GetSomeStringValue(Value)
Why is this not returning the entire string?
Note: this answer was originally written by the OP, Kibbee, as a self-answer. However, it was written in the body of the question, not as an actual separate answer. Since the OP has refused repeated requests by other users, including a moderator, to repost in accordance with site rules, I'm reposting it myself.
After trying a hundred different things, refactoring my code, stepping through the code in the debugger many times, and even having a co-worker look into the problem, I finally, in a flash of genius, discovered the answer.
At some point when I was refactoring the code, I changed the function to get rid of the Value parameter, leaving it as follows:
Public Function GetSomeStringValue() As String
... Code Goes here
Return Some_Multicharacter_String
End Function
However, I neglected to remove the parameter that I was passing in when calling the function:
SomeStringValue = GetSomeStringValue(Value)
The compiler didn't complain because it interpreted what I was doing as calling the function without brackets, which is a legacy feature from the VB6 days. Then, the Value parameter transformed into the array index of the string (aka character array) that was returned from the function.
So I removed the parameter, and everything worked fine:
SomeStringValue = GetSomeStringValue()
I'm posting this so that other people will recognize the problem when/if they ever encounter it, and are able to solve it much more quickly than I did. It took quite a while for me to solve, and I hope I can save others some time.