Eval function vb.net

[Maurice]

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

[Armin Zingler]

"Maurice" <hm*****@nospam.nospam> schrieb

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"

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

[Maurice]

"Armin Zingler" <az*******@freenet.de> wrote in
news:uD**************@TK2MSFTNGP12.phx.gbl:

http://msdn.microsoft.com/library/de...y/en-us/cpguid
e/html/cpconemittingdynamicassemblies.asp

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.

[Armin Zingler]

"Maurice" <hm*****@nospam.nospam> schrieb

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.

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

[Maurice]

"Armin Zingler" <az*******@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.

[CMM]

Look into Activator.CreateInstance(). This has been asked before. Do a
search for more detailed examples.
--
-C. Moya
www.cmoya.com
"Maurice" <hm*****@nospam.nospam> wrote in message
news:Xn****************************@194.109.133.24 2...

"Armin Zingler" <az*******@freenet.de> wrote in
news:uD**************@TK2MSFTNGP12.phx.gbl:

http://msdn.microsoft.com/library/de...y/en-us/cpguid
e/html/cpconemittingdynamicassemblies.asp

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.

[Armin Zingler]

"Maurice" <hm*****@nospam.nospam> schrieb

"Armin Zingler" <az*******@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.

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

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

[Herfried K. Wagner [MVP]]

"Maurice" <hm*****@nospam.nospam> schrieb:

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"

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/>

[Charles Law]

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" <hm*****@nospam.nospam> wrote in message
news:Xn****************************@194.109.133.24 2...

"Armin Zingler" <az*******@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.

[Cor Ligthert [MVP]]

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" <bl***@nowhere.com> schreef in bericht
news:%2****************@TK2MSFTNGP09.phx.gbl...

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" <hm*****@nospam.nospam> wrote in message
news:Xn****************************@194.109.133.24 2...

"Armin Zingler" <az*******@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.

[Charles Law]

Hi Cor

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

Charles
"Cor Ligthert [MVP]" <no************@planet.nl> wrote in message
news:ui**************@TK2MSFTNGP10.phx.gbl...

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" <bl***@nowhere.com> schreef in bericht
news:%2****************@TK2MSFTNGP09.phx.gbl...

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" <hm*****@nospam.nospam> wrote in message
news:Xn****************************@194.109.133.24 2...

"Armin Zingler" <az*******@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.

[Cor Ligthert [MVP]]

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

[Charles Law]

Hi Cor

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

Charles
"Cor Ligthert [MVP]" <no************@planet.nl> wrote in message
news:ua**************@TK2MSFTNGP14.phx.gbl...

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

[Maurice]

"Cor Ligthert [MVP]" <no************@planet.nl> wrote in
news:ua**************@TK2MSFTNGP14.phx.gbl:

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

Hi Charles, Cor,

thanks for the good support!

I will try this one out.
Maurice