Eval function vb.net

Hi,

is it possible to enter a string in code in VB.NET 2005 which will be
executed as a codeline during runtime?

i.e. I want to declare a new form depending on the string:
"Dim frm as new frmTest"

Thanx

"Maurice" <hmoviat@nospam.nospam> schrieb[color=blue]
> Hi,
>
> is it possible to enter a string in code in VB.NET 2005 which will
> be executed as a codeline during runtime?
>
> i.e. I want to declare a new form depending on the string:
> "Dim frm as new frmTest"[/color]

This line is to be part of which method, class, namespace, assembly?
Maybe the answers to the 2 questions above help.

Or: (Framework 1.1)
http://msdn.microsoft.com/library/de...assemblies.asp

Armin

"Armin Zingler" <az.nospam@freenet.de> wrote in
news:uDJYz8iNGHA.3856@TK2MSFTNGP12.phx.gbl:
[color=blue]
> http://msdn.microsoft.com/library/de...y/en-us/cpguid
> e/html/cpconemittingdynamicassemblies.asp[/color]

Hi Armin,

I have 2 different forms inside my project:
frmTest
frmCompany

I can declare a new form by using the code:
dim frm as new frmTest
OR
dim frm as new frmCompany

What I want is that when I have a string with the form name (strFormName) I
can use this string to declare the new form.

strEval = "Dim frm as new " & strFormName

Something like this. So the string above (strEval) will be executed as a
line of code.

"Maurice" <hmoviat@nospam.nospam> schrieb[color=blue]
> Hi Armin,
>
> I have 2 different forms inside my project:
> frmTest
> frmCompany
>
> I can declare a new form by using the code:
> dim frm as new frmTest
> OR
> dim frm as new frmCompany
>
> What I want is that when I have a string with the form name
> (strFormName) I can use this string to declare the new form.
>
> strEval = "Dim frm as new " & strFormName
>
> Something like this. So the string above (strEval) will be executed
> as a line of code.[/color]

Creating an object by class name has been asked three times in a row, that's
why I pointed to the previous two questions and answers.

Why do you have the class name in a string? Often this is not necessary:

Dim frm as form

select case value
case This
frm = new frmTest
case That
frm = new frmCompany
end select

frm.show

Armin

"Armin Zingler" <az.nospam@freenet.de> wrote in news:OrGv#YjNGHA.428
@tk2msftngp13.phx.gbl:
[color=blue]
> Creating an object by class name[/color]

Hi Armin,

sorry, indeed creating an object by class name.

It's possible that in future some names may change and I don;t want to
change this function then. That's why I don't want a select case statement
to declare a new form.

But isn't there something like the Eval function in VBScript that you can
use?

i.e.:
Dim intA as integer, intB as integer, intC as integer

intA = 5
intB = 10
Eval("intC = intA * intB")

The string value "intC = intA * intB" would then be executed as code and
intC would have the value 50.

Look into Activator.CreateInstance(). This has been asked before. Do a
search for more detailed examples.

--
-C. Moya
www.cmoya.com
"Maurice" <hmoviat@nospam.nospam> wrote in message
news:Xns9770A5BB9E1ACmauricemertens@194.109.133.24 2...[color=blue]
> "Armin Zingler" <az.nospam@freenet.de> wrote in
> news:uDJYz8iNGHA.3856@TK2MSFTNGP12.phx.gbl:
>[color=green]
>> http://msdn.microsoft.com/library/de...y/en-us/cpguid
>> e/html/cpconemittingdynamicassemblies.asp[/color]
>
> Hi Armin,
>
> I have 2 different forms inside my project:
> frmTest
> frmCompany
>
> I can declare a new form by using the code:
> dim frm as new frmTest
> OR
> dim frm as new frmCompany
>
> What I want is that when I have a string with the form name (strFormName)
> I
> can use this string to declare the new form.
>
> strEval = "Dim frm as new " & strFormName
>
> Something like this. So the string above (strEval) will be executed as a
> line of code.
>
>
>
>
>
>[/color]

"Maurice" <hmoviat@nospam.nospam> schrieb[color=blue]
> "Armin Zingler" <az.nospam@freenet.de> wrote in news:OrGv#YjNGHA.428
> @tk2msftngp13.phx.gbl:
>[color=green]
> > Creating an object by class name[/color]
>
> Hi Armin,
>
> sorry, indeed creating an object by class name.
>
> It's possible that in future some names may change and I don;t want
> to change this function then. That's why I don't want a select case
> statement to declare a new form.[/color]

A class name usually doesn't change, and if it changes we have to change the
code. If you change a variable name you also have to change the code
accessing the variable. Reflection is not a replacement for this.
[color=blue]
> But isn't there something like the Eval function in VBScript that
> you can use?[/color]

No.

VB.Net is not an interpreter. Source code is compiled into an executable
(IL-Code), then to native assembler code by the JIT-Compiler. Source code
has a structure. Executable commands are part of procedures. Procedures are
members of classes, and classes are contained in assemblies. That's the
structure of an application. You can not place a string into nowhere without
any context.

If you dynamically want to create an application, you must supply this
structure. That's why I provided the link in my first message, but I was
actually looking for this one:
http://msdn.microsoft.com/library/en...elanguages.asp

Armin

"Maurice" <hmoviat@nospam.nospam> schrieb:[color=blue]
> is it possible to enter a string in code in VB.NET 2005 which will be
> executed as a codeline during runtime?
>
> i.e. I want to declare a new form depending on the string:
> "Dim frm as new frmTest"[/color]

Build a Custom .NET "EVAL" Provider
<URL:http://www.eggheadcafe.com/articles/20030908.asp>

Runtime Compilation (A .NET eval statement)
<URL:http://www.codeproject.com/dotnet/evaluator.asp>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

Hi Maurice

Here is something I use

<code>
Public NotInheritable Class Evaluator

Private Shared WithEvents m_ScriptControl As
MSScriptControl.ScriptControlClass

Shared Sub New()

m_ScriptControl = New MSScriptControl.ScriptControlClass

m_ScriptControl.Language = "VBScript"
m_ScriptControl.AllowUI = False

End Sub

Public Shared Function Evaluate(ByVal s As String, ByVal decimalPlaces
As Integer) As Double

Return Decimal.Round(Convert.ToDecimal(Evaluate(s)), decimalPlaces)

End Function

Public Shared Function Evaluate(ByVal s As String) As Double

Dim r As Double

m_ScriptControl.Reset()

' Example of executing code
''m_ScriptControl.ExecuteStatement("Dim m")
''m_ScriptControl.ExecuteStatement("m = 5")

' Example of manipulating a form
''m_ScriptControl.AddObject("DotnetForm", Me)
''m_ScriptControl.ExecuteStatement("dotnetform.wid th =
dotnetform.width + 10")

Try
r = CDbl(m_ScriptControl.Eval(s))

Catch ex As Exception
Dim ee As EvaluationException

ee = New EvaluationException(ex.Message)

ee.Description = m_ScriptControl.Error.Description
ee.Column = m_ScriptControl.Error.Column
ee.Number = m_ScriptControl.Error.Number
ee.Source = m_ScriptControl.Error.Source
ee.Text = m_ScriptControl.Error.Text

Throw ee

End Try

Return r

End Function

End Class
</code>

I call Evaluator.Evaluate(...) with a string that I want to evaluate,
optionally with a number of decimal places. EvaluationException is my custom
exception class, but you could make up your own.

HTH

Charles

"Maurice" <hmoviat@nospam.nospam> wrote in message
news:Xns9770B2725FE78mauricemertens@194.109.133.24 2...[color=blue]
> "Armin Zingler" <az.nospam@freenet.de> wrote in news:OrGv#YjNGHA.428
> @tk2msftngp13.phx.gbl:
>[color=green]
>> Creating an object by class name[/color]
>
> Hi Armin,
>
> sorry, indeed creating an object by class name.
>
> It's possible that in future some names may change and I don;t want to
> change this function then. That's why I don't want a select case statement
> to declare a new form.
>
> But isn't there something like the Eval function in VBScript that you can
> use?
>
> i.e.:
> Dim intA as integer, intB as integer, intC as integer
>
> intA = 5
> intB = 10
> Eval("intC = intA * intB")
>
> The string value "intC = intA * intB" would then be executed as code and
> intC would have the value 50.
>
>
>[/color]

Charles,

Do you mind if I test your class and than set it on our (VB-Tips) website,
this was in my opinion as well the way to go and I was intended to try it
some day.

(With telling who it made of course)

Cor

"Charles Law" <blank@nowhere.com> schreef in bericht
news:%23mviJK5NGHA.3196@TK2MSFTNGP09.phx.gbl...[color=blue]
> Hi Maurice
>
> Here is something I use
>
> <code>
> Public NotInheritable Class Evaluator
>
> Private Shared WithEvents m_ScriptControl As
> MSScriptControl.ScriptControlClass
>
> Shared Sub New()
>
> m_ScriptControl = New MSScriptControl.ScriptControlClass
>
> m_ScriptControl.Language = "VBScript"
> m_ScriptControl.AllowUI = False
>
> End Sub
>
> Public Shared Function Evaluate(ByVal s As String, ByVal decimalPlaces
> As Integer) As Double
>
> Return Decimal.Round(Convert.ToDecimal(Evaluate(s)), decimalPlaces)
>
> End Function
>
> Public Shared Function Evaluate(ByVal s As String) As Double
>
> Dim r As Double
>
> m_ScriptControl.Reset()
>
> ' Example of executing code
> ''m_ScriptControl.ExecuteStatement("Dim m")
> ''m_ScriptControl.ExecuteStatement("m = 5")
>
> ' Example of manipulating a form
> ''m_ScriptControl.AddObject("DotnetForm", Me)
> ''m_ScriptControl.ExecuteStatement("dotnetform.wid th =
> dotnetform.width + 10")
>
> Try
> r = CDbl(m_ScriptControl.Eval(s))
>
> Catch ex As Exception
> Dim ee As EvaluationException
>
> ee = New EvaluationException(ex.Message)
>
> ee.Description = m_ScriptControl.Error.Description
> ee.Column = m_ScriptControl.Error.Column
> ee.Number = m_ScriptControl.Error.Number
> ee.Source = m_ScriptControl.Error.Source
> ee.Text = m_ScriptControl.Error.Text
>
> Throw ee
>
> End Try
>
> Return r
>
> End Function
>
> End Class
> </code>
>
> I call Evaluator.Evaluate(...) with a string that I want to evaluate,
> optionally with a number of decimal places. EvaluationException is my
> custom exception class, but you could make up your own.
>
> HTH
>
> Charles
>
>
> "Maurice" <hmoviat@nospam.nospam> wrote in message
> news:Xns9770B2725FE78mauricemertens@194.109.133.24 2...[color=green]
>> "Armin Zingler" <az.nospam@freenet.de> wrote in news:OrGv#YjNGHA.428
>> @tk2msftngp13.phx.gbl:
>>[color=darkred]
>>> Creating an object by class name[/color]
>>
>> Hi Armin,
>>
>> sorry, indeed creating an object by class name.
>>
>> It's possible that in future some names may change and I don;t want to
>> change this function then. That's why I don't want a select case
>> statement
>> to declare a new form.
>>
>> But isn't there something like the Eval function in VBScript that you can
>> use?
>>
>> i.e.:
>> Dim intA as integer, intB as integer, intC as integer
>>
>> intA = 5
>> intB = 10
>> Eval("intC = intA * intB")
>>
>> The string value "intC = intA * intB" would then be executed as code and
>> intC would have the value 50.
>>
>>
>>[/color]
>
>[/color]

Hi Cor

Please feel free. I'd be honoured :-)

Charles

"Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message
news:uiIv2k5NGHA.3732@TK2MSFTNGP10.phx.gbl...[color=blue]
> Charles,
>
> Do you mind if I test your class and than set it on our (VB-Tips) website,
> this was in my opinion as well the way to go and I was intended to try it
> some day.
>
> (With telling who it made of course)
>
> Cor
>
> "Charles Law" <blank@nowhere.com> schreef in bericht
> news:%23mviJK5NGHA.3196@TK2MSFTNGP09.phx.gbl...[color=green]
>> Hi Maurice
>>
>> Here is something I use
>>
>> <code>
>> Public NotInheritable Class Evaluator
>>
>> Private Shared WithEvents m_ScriptControl As
>> MSScriptControl.ScriptControlClass
>>
>> Shared Sub New()
>>
>> m_ScriptControl = New MSScriptControl.ScriptControlClass
>>
>> m_ScriptControl.Language = "VBScript"
>> m_ScriptControl.AllowUI = False
>>
>> End Sub
>>
>> Public Shared Function Evaluate(ByVal s As String, ByVal decimalPlaces
>> As Integer) As Double
>>
>> Return Decimal.Round(Convert.ToDecimal(Evaluate(s)),
>> decimalPlaces)
>>
>> End Function
>>
>> Public Shared Function Evaluate(ByVal s As String) As Double
>>
>> Dim r As Double
>>
>> m_ScriptControl.Reset()
>>
>> ' Example of executing code
>> ''m_ScriptControl.ExecuteStatement("Dim m")
>> ''m_ScriptControl.ExecuteStatement("m = 5")
>>
>> ' Example of manipulating a form
>> ''m_ScriptControl.AddObject("DotnetForm", Me)
>> ''m_ScriptControl.ExecuteStatement("dotnetform.wid th =
>> dotnetform.width + 10")
>>
>> Try
>> r = CDbl(m_ScriptControl.Eval(s))
>>
>> Catch ex As Exception
>> Dim ee As EvaluationException
>>
>> ee = New EvaluationException(ex.Message)
>>
>> ee.Description = m_ScriptControl.Error.Description
>> ee.Column = m_ScriptControl.Error.Column
>> ee.Number = m_ScriptControl.Error.Number
>> ee.Source = m_ScriptControl.Error.Source
>> ee.Text = m_ScriptControl.Error.Text
>>
>> Throw ee
>>
>> End Try
>>
>> Return r
>>
>> End Function
>>
>> End Class
>> </code>
>>
>> I call Evaluator.Evaluate(...) with a string that I want to evaluate,
>> optionally with a number of decimal places. EvaluationException is my
>> custom exception class, but you could make up your own.
>>
>> HTH
>>
>> Charles
>>
>>
>> "Maurice" <hmoviat@nospam.nospam> wrote in message
>> news:Xns9770B2725FE78mauricemertens@194.109.133.24 2...[color=darkred]
>>> "Armin Zingler" <az.nospam@freenet.de> wrote in news:OrGv#YjNGHA.428
>>> @tk2msftngp13.phx.gbl:
>>>
>>>> Creating an object by class name
>>>
>>> Hi Armin,
>>>
>>> sorry, indeed creating an object by class name.
>>>
>>> It's possible that in future some names may change and I don;t want to
>>> change this function then. That's why I don't want a select case
>>> statement
>>> to declare a new form.
>>>
>>> But isn't there something like the Eval function in VBScript that you
>>> can
>>> use?
>>>
>>> i.e.:
>>> Dim intA as integer, intB as integer, intC as integer
>>>
>>> intA = 5
>>> intB = 10
>>> Eval("intC = intA * intB")
>>>
>>> The string value "intC = intA * intB" would then be executed as code and
>>> intC would have the value 50.
>>>
>>>
>>>[/color]
>>
>>[/color]
>
>[/color]

Charles,

I made it a little bit more simple as sample. Do you agree with this?

http://www.vb-tips.com/default.aspx?...1-2b03e1a439ae

Cor

Hi Cor

Yes, indeed. It is neat enough to demonstrate the idea, and people can add
frills as they wish.

Charles

"Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message
news:ua$Ue27NGHA.3284@TK2MSFTNGP14.phx.gbl...[color=blue]
> Charles,
>
> I made it a little bit more simple as sample. Do you agree with this?
>
> http://www.vb-tips.com/default.aspx?...1-2b03e1a439ae
>
>
> Cor
>[/color]

"Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in
news:ua$Ue27NGHA.3284@TK2MSFTNGP14.phx.gbl:
[color=blue]
> Charles,
>
> I made it a little bit more simple as sample. Do you agree with this?
>
> http://www.vb-tips.com/default.aspx?...-86d1-2b03e1a4
> 39ae
>
>
> Cor
>
>[/color]

Hi Charles, Cor,

thanks for the good support!

I will try this one out.

Maurice

Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

re: Eval function vb.net

Similar Visual Basic .NET bytes

/bytes/development

/bytes/it

/bytes/about