I'm trying to use the value of a string variable to become the name of my new variable. For example see, below code. Reason I'm doing this is I have a text file containing the names of the variables I need to create objects for. Perhaps there is another way to do this?
Dim mystring As String
mystring = "Variablename"
'dim "Variablename" as object
How about using a collection? The key of the items in the collection would be your variable name, and the value of the items in the collection are your variables.
Here is an example of creating a class with custom properties. If you do want to go this route, this should help you:
' Note: There is no root namespace in the project properties
Imports System.CodeDom.Compiler
Imports System.Reflection
Namespace Foo
Module Module1
Sub Main()
Dim instance = createInstance({"Prap", "Prep", "Prip", "Prop", "Prup"})
instance.Prap = "Prappy"
Console.WriteLine(instance.Prap)
End Sub
Private Function createInstance(propertyNames As IEnumerable(Of String)) As Object
Dim codeProvider As New VBCodeProvider()
Dim codeCompiler As ICodeCompiler = codeProvider.CreateCompiler()
Dim compilerParameters As New CompilerParameters()
compilerParameters.CompilerOptions = "/target:library"
Dim code =
"NameSpace Foo" & Environment.NewLine &
" Partial Public Class Bar" & Environment.NewLine
For Each name In propertyNames
code &=
String.Format(" Public Property {0} As String", name) & Environment.NewLine
Next
code &= " End Class" & Environment.NewLine &
"End Namespace"
Console.WriteLine("Code to compile:")
Console.WriteLine(code)
Dim result = codeCompiler.CompileAssemblyFromSource(compilerParameters, code)
If result.Errors.HasErrors Then
Console.WriteLine(result.Errors.OfType(Of CompilerError).Aggregate(Of String)("Errors:", Function(e1, e2) e1 & ", " & e2.ErrorText))
Return Nothing
Else
Console.WriteLine("Success")
Dim type As Type = result.CompiledAssembly.GetType("Foo.Bar")
Dim instance = Activator.CreateInstance(type)
Return instance
End If
End Function
End Module
End Namespace
Output:
Code to compile:
NameSpace Foo
Partial Public Class Bar
Public Property Prap As String
Public Property Prep As String
Public Property Prip As String
Public Property Prop As String
Public Property Prup As String
End Class
End Namespace
Success
Prappy
Now, you could also build the class with different property types than String, which is hard-coded. Just include it in the arguments either as a separate array, or you could use a Tuple or Dictionary etc. Good luck!
Related
I am developing a server-side scripting language which I intend to use on my private server. It is similar to PHP, and I know that I could easily use PHP instead but I'm just doing some programming for fun.
The syntax of basic commands in my language is as follows:
command_name "parameter1" : "parameter2" : "parameter3"
But it can also be like this when I want to join values for a parameter:
command_name "parameter1" : "param" & "eter2" : "par" & "amet" & "er3"
How would I go about parsing a string like the ones shown above (it will be perfectly typed, no syntax errors) to an object that has these properties
Custom class "Request"
Property "Command" as String, should be the "command_name" part
Property "Parameters" as String(), should be an array of Parameter objects
Shared Function FromString(s As String) as Request, this should accept a string in the language above and parse it to a Request object
Custom class "Parameter"
Property "Segments" as String(), for example "para", "mete", and "r3"
Sub New(ParamArray s as String()), this is how it should be generated from the code
It should be done in VB.NET and I am a moderate level programmer, so even if you just have an idea of how to attack this then please share it with me. I am very new to parsing complex data like this so I need a lot of help. Thanks so much!
Here is another method that is simpler.
Module Module1
Sub Main()
Dim inputs As String() = {"command_name ""parameter1"" : ""parameter2"" : ""parameter3""", "command_name ""parameter1"" : ""param"" & ""eter2"" : ""par"" & ""amet"" & ""er3"""}
For Each _input As String In inputs
Dim commandStr As String = _input.Substring(0, _input.IndexOf(" ")).Trim()
Dim parameters As String = _input.Substring(_input.IndexOf(" ")).Trim()
Dim parametersA As String() = parameters.Split(":".ToCharArray(), StringSplitOptions.RemoveEmptyEntries).Select(Function(x) x.Trim()).ToArray()
Dim parametersB As String()() = parametersA.Select(Function(x) x.Split("&".ToCharArray(), StringSplitOptions.RemoveEmptyEntries).Select(Function(y) y.Trim(" """.ToCharArray())).ToArray()).ToArray()
Dim newCommand As New Command() With {.name = commandStr, .parameters = parametersB.Select(Function(x) New Parameter(x)).ToArray()}
Command.commands.Add(newCommand)
Next (_input)
Dim z = Command.commands
End Sub
End Module
Public Class Command
Public Shared commands As New List(Of Command)
Public name As String
Public parameters As Parameter()
End Class
Public Class Parameter
Sub New()
End Sub
Sub New(names As String())
Me.names = names
End Sub
Public names As String()
End Class
I figured it out myself
Module Module1
Sub Main()
Dim r As Request = Request.Parse(Console.ReadLine())
Console.WriteLine("The type of request is " & r.Name)
For Each p As Parameter In r.Parameters
Console.WriteLine("All segments inside of parameter " & r.Parameters.IndexOf(p).ToString)
For Each s As String In p.Segments
Console.WriteLine(" Segment " & p.Segments.IndexOf(s).ToString & " is " & s)
Next
Next
Main()
End Sub
Public Class Request
Public Name As String
Public Parameters As New List(Of Parameter)
Public Shared Function Parse(line As String)
Dim r As New Request
r.Name = line.Split(" ")(0)
Dim u As String = line.Substring(line.IndexOf(" "), line.Length - line.IndexOf(" "))
Dim p As String() = u.Split(":")
For Each n As String In p
Dim b As String() = n.Split("&")
Dim e As New List(Of String)
For Each m As String In b
Dim i As Integer = 0
Do Until i > m.Length - 1
If m(i) = ControlChars.Quote Then
Dim s As String = ""
i += 1
Do Until i > m.Length - 1 Or m(i) = ControlChars.Quote
s &= m(i)
i += 1
Loop
e.Add(s)
End If
i += 1
Loop
Next
r.Parameters.Add(New Parameter(e.ToArray))
Next
Return r
End Function
End Class
Public Class Parameter
Public Segments As New List(Of String)
Public Sub New(ParamArray s As String())
Segments = s.ToList
End Sub
End Class
End Module
I am trying to reference the name of a variable as a string. I have a list of global variables
Public gvHeight As String = Blank
Public gvWeight As String = Blank
Public gvAge As String = Blank
I need to reference the name of the variables for an external API call. I am trying to avoid specific code per variable, instead allow me to add a new variable and everything reference correctly. I already have the rest of the code to deal with the name as a string.
example:
public Height as string
public weight as string
public age as string
[elsewhere in code]
for each var as string in {public variables}
CallToAPI(var.name) 'needs to send "height" "weight" or "age" but there are a lot so hardcoding is not a good solution
edited for example
You need to find the public fields through Reflection.
Having an example dll compiled from this source-code:
Public Class Class1
Public Field1 As String = "value 1"
Public Field2 As String = "value 2"
Public Field3 As Integer
End Class
Then you could do this:
' The library path.
Dim libpath As String = "...\ClassLibrary1.dll"
' The assembly.
Dim ass As Assembly = Assembly.LoadFile(libpath)
' The Class1 type. (full namespace is required)
Dim t As Type = ass.GetType("ClassLibrary1.Class1", throwOnError:=True)
' The public String fields in Class1.
Dim strFields As FieldInfo() =
(From f As FieldInfo In t.GetFields(BindingFlags.Instance Or BindingFlags.Public)
Where f.FieldType Is GetType(String)
).ToArray
' A simple iteration over the fields to print their names.
For Each field As FieldInfo In strFields
Console.WriteLine(field.Name)
Next strField
If all your variables are of the same type (here strings), you can use a Dictionary...
Public MyModule
Private myVars As Dictionary(Of String, String)
Public Function CallToAPI(VarName As String) As String
If myVars.ContainsKey(VarName) Then
Return myVars(VarName)
End If
Return ""
End Function
End Module
And somewhere else in your external code
Module TestModule
Public Sub Test()
Dim myVar = MyModule.CallToAPI("test")
End Sub
End Module
Now if your variables aren't the same, then you must use Reflection... and that's where the fun begins...
In the code below, I want to be able to access the enteredusername and enteredpassword variables from any sub routine. How would I accomplish this?
Using rdr As New FileIO.TextFieldParser("f:\Computing\Spelling Bee\stdnt&staffdtls.csv")
rdr.TextFieldType = FieldType.Delimited
rdr.Delimiters = New String() {","c}
item = rdr.ReadFields()
End Using
Console.Write("Username: ")
enteredusername = Console.ReadLine
Console.Write("Password: ")
Dim info As ConsoleKeyInfo
Do
info = Console.ReadKey(True)
If info.Key = ConsoleKey.Enter Then
Exit Do
End If
If info.Key = ConsoleKey.Backspace AndAlso enteredpassword.Length > 0 Then
enteredpassword = enteredpassword.Substring(0, enteredpassword.Length - 1)
Console.Write(vbBack & " ")
Console.CursorLeft -= 1
Else
enteredpassword &= info.KeyChar
Console.Write("*"c)
End If
Loop
Dim foundItem() As String = Nothing
For Each line As String In File.ReadAllLines("f:\Computing\Spelling Bee\stdnt&staffdtls.csv")
Dim item() As String = line.Split(","c)
If (enteredusername = item(0)) And (enteredpassword = item(1)) Then
foundItem = item
Exit For
End If
Next
To allow ALL classes within your program access the variable, you need to make it class-level and define it with Public and Shared.
Demonstration:
Public Class MainClass
Public Shared enteredusername As String
Public Shared enteredpassword As String
Private Sub SomeSub()
' Some Code ...
' You can access it here:
enteredusername = "something"
enteredpassword = "something else"
' ... More Code ...
End Sub
End Class
Public Class AnotherClass
'Also, please note, that this class can also be in another file.
Private Sub AnotherSub()
' Some Code ...
' You can also access the variable here, but you need to specify what class it is from, like so:
Console.WriteLine(MainClass.enteredusername)
Console.WriteLine(MainClass.enteredpassword)
' ... More Code ...
End Sub
End Class
Also, on a separate note, the Public and Shared modifiers can also be used on methods. If you make a method Private or don't specify anything, the method will only be accessible from methods in the same class. If you use only Public, other classes can access the method, but they will need to create a instance of the class, like so:
Dim AC As New AnotherClass
AC.AnotherSub()
If you use both the Public and the Shared modifiers, other classes will be able to access the method directly, without creating a new instance. But, you must note, that Shared methods cannot access non-Shared methods or variables. Other classes can access Public Shared methods like so:
AnotherClass.AnotherSub()
It depends on the scope. If you want all of the subroutines in the current class to be able to access them then make them a field of the class
Class TheClassName
Dim enteredusername As String
Dim enteredpassword As String
...
End Class
If you want all subroutines in all classes and modules to be able to access them then make them a module level field
Module TheModuleName
Dim enteredusername As String
Dim enteredpassword As String
...
End Module
I recommend against this approach though. Sure it's easier in the short term because it requires less ceremony and thought on the uses of the values. But long term it serves to reduce the maintainability of your code base
How can I get the name of the object that was passed byref into a method?
Example:
Dim myobject as object
sub mymethod(byref o as object)
debug.print(o.[RealName!!!!])
end sub
sub main()
mymethod(myobject)
'outputs "myobject" NOT "o"
end sub
I'm using this for logging. I use one method multiple times and it would be nice to log the name of the variable that I passed to it. Since I'm passing it byref, I should be able to get this name, right?
For minitech who provided the answer:
This would give you the parameter name in the method and it's type, but not the name of the variable that was passed byref.
using system.reflection
Dim mb As MethodBase = MethodInfo.GetCurrentMethod()
For Each pi As ParameterInfo In mb.GetParameters()
Debug.Print("Parameter: Type={0}, Name={1}", pi.ParameterType, pi.Name)
Next
If you put that in "mymethod" above you'd get "o" and "Object".
That's impossible. Names of variables are not stored in IL, only names of class members or namespace classes. Passing it by reference makes absolutely zero difference. You wouldn't even be able to get it to print out "o".
Besides, why would you ever want to do that?
Alternatively you could get the 'Type' of the object using reflection.
Example: (Use LinqPad to execute)
Sub Main
Dim myDate As DateTime = DateTime.Now
MyMethod(myDate)
Dim something As New Something
MyMethod(something)
End Sub
Public Class Something
Public Sub New
Me.MyProperty = "Hello"
End Sub
Public Property MyProperty As String
End Class
Sub MyMethod(Byref o As Object)
o.GetType().Name.Dump()
End Sub
Sorry to say, but this is your solution. I left (ByVal o As Object) in the method signature in case you're doing more with it.
Sub MyMethod(ByVal o As Object, ByVal name As String)
Debug.Print(name)
End Sub
Sub Main()
MyMethod(MyObject, "MyObject")
End Sub
Alternatively you could create an interface, but this would only allow you to use MyMethod with classes you design. You can probably do more to improve it, but as this code stands you can only set the RealName at creation.
Interface INamedObject
Public ReadOnly Property RealName As String
End Interface
Class MyClass
Implements INamedObject
Public Sub New(ByVal RealName As String)
_RealName = RealName
End Sub
Private ReadOnly Property RealName As String Implements INamedObject.RealName
Get
Return _RealName
End Get
End Property
Private _RealName As String
End Class
Module Main
Sub MyMethod(ByVal o As INamedObject)
Debug.Print(o.RealName)
End Sub
Sub Main()
Dim MyObject As New MyClass("MyObject")
MyMethod(MyObject)
End Sub
End Module
If your program is still in the same place relative to the code that made it, this may work:
' First get the Stack Trace, depth is how far up the calling tree you want to go
Dim stackTrace As String = Environment.StackTrace
Dim depth As Integer = 4
' Next parse out the location of the code
Dim delim As Char() = {vbCr, vbLf}
Dim traceLine As String() = stackTrace.Split(delim, StringSplitOptions.RemoveEmptyEntries)
Dim filePath As String = Regex.Replace(traceLine(depth), "^[^)]+\) in ", "")
filePath = Regex.Replace(filePath, ":line [0-9]+$", "")
Dim lineNumber As String = Regex.Replace(traceLine(depth), "^.*:line ", "")
' Now read the file
Dim program As String = __.GetStringFromFile(filePath, "")
' Next parse out the line from the class file
Dim codeLine As String() = program.Split(delim)
Dim originLine As String = codeLine(lineNumber * 2 - 2)
' Now get the name of the method doing the calling, it will be one level shallower
Dim methodLine As String = Regex.Replace(traceLine(depth - 1), "^ at ", "")
Dim methodName = Regex.Replace(methodLine, "\(.*\).*$", "")
methodName = Regex.Replace(methodName, "^.*\.", "")
' And parse out the variables from the method
Dim variables As String = Regex.Replace(originLine, "^.*" & methodName & "\(", "")
variables = Regex.Replace(variables, "\).*$", "")
You control the depth that this digs into the stack trace with the depth parameter. 4 works for my needs. You might need to use a 1 2 or 3.
This is the apparently how Visual Basic controls handle the problem.
They have a base control class that in addition to any other common properties these controls may have has a name property.
For Example:
Public MustInherit Class NamedBase
Public name As String
End Class
Public Class MyNamedType
Inherits NamedBase
public Value1 as string
public Value2 as Integer
End Class
dim x as New MyNamedType
x.name = "x"
x.Value1 = "Hello, This variable is name 'x'."
x.Value2 = 75
MySubroutine(x)
public sub MySubroutine(y as MyNamedType)
debug.print("My variable's name is: " & y.name)
end sub
The output in the intermediate window should be:
My variable's name is: x
Hi
I am working on a project where my class has to execute VB code provided by the user, to make it simple i am trying to recreate my own eval function, i am using the following code i found on the web to do this task
Imports Microsoft.VisualBasic
Imports System
Imports System.Text
Imports System.CodeDom.Compiler
Imports System.Reflection
Imports System.IO
Namespace PAB.Util
Public Class EvalProvider
Public Function VS_Eval(ByVal vbCode As String) As Object
Dim c As VBCodeProvider = New VBCodeProvider
Dim icc As ICodeCompiler = c.CreateCompiler()
Dim cp As CompilerParameters = New CompilerParameters
cp.ReferencedAssemblies.Add("system.dll")
cp.ReferencedAssemblies.Add("system.xml.dll")
cp.ReferencedAssemblies.Add("system.data.dll")
' Sample code for adding your own referenced assemblies
'cp.ReferencedAssemblies.Add("c:\yourProjectDir\bin\YourBaseClass.dll")
'cp.ReferencedAssemblies.Add("YourBaseclass.dll")
cp.CompilerOptions = "/t:library"
cp.GenerateInMemory = True
Dim sb As StringBuilder = New StringBuilder("")
sb.Append("Imports System" & vbCrLf)
sb.Append("Imports System.Xml" & vbCrLf)
sb.Append("Imports System.Data" & vbCrLf)
sb.Append("Imports System.Data.SqlClient" & vbCrLf)
sb.Append("Namespace PAB " & vbCrLf)
sb.Append("Class PABLib " & vbCrLf)
sb.Append("public function EvalCode() as Object " & vbCrLf)
'sb.Append("YourNamespace.YourBaseClass thisObject = New YourNamespace.YourBaseClass()")
sb.Append(vbCode & vbCrLf)
sb.Append("End Function " & vbCrLf)
sb.Append("End Class " & vbCrLf)
sb.Append("End Namespace" & vbCrLf)
Debug.WriteLine(sb.ToString()) ' look at this to debug your eval string
Dim cr As CompilerResults = icc.CompileAssemblyFromSource(cp, sb.ToString())
Dim a As System.Reflection.Assembly = cr.CompiledAssembly
Dim o As Object
Dim mi As MethodInfo
o = a.CreateInstance("PAB.PABLib")
Dim t As Type = o.GetType()
mi = t.GetMethod("EvalCode")
Dim s As Object
s = mi.Invoke(o, Nothing)
Return s
End Function
End Class
End Namespace
The problem with code is that it can't access any variables or there values, so i have decided to get the variable names, there values types and there types dynamically and recreate them in the class that is being created dynamically.
Please suggest a way to get the variable names there types and values in the current class or method, so that i can recreate them, and execute the user passed code, the user knows what variables are in the current class or method and there datatypes but he don't know there values as they may have changed, so he can't initialize them.
Is there a way to do this, this code will be called in an asp.net page on page_load event, the code passed by the user is stored in the variable vbCode that is passed as a parameter.
If there is any other method to do this, please suggest
Thank you
I have finally found the solution of how to get the variables and values of the current instance of a class.
using System.Reflection; it is very easy to achieve, all you have to write is the following line:
Dim fields As FieldInfo() = Me.GetType().GetFields()
For Each fld As FieldInfo In fields
Dim name As String = fld.Name
Dim value = fld.GetValue(Me)
Dim typ As Type = fld.FieldType
Next
Note : It only works for public variables
This may help you?