Is it event possible to import text as code, then add it in a sub in vb.net? If I have a .txt file filled with code can I import it programatically (by a button)?
What I need is to make vb.net to accept that script (txt file), and use it to declare variables and make functions/subs - that's all I need to.
You can do this kind of thing using the CodeDom objects. The CodeDom objects allow you to dynamically generate assemblies at run-time. For instance, if you make an interface
Public Interface IScript
Property Variable1 As String
Sub DoWork()
End Interface
Then, you create a method, like this:
Imports Microsoft.VisualBasic
Imports System.CodeDom.Compiler
' ...
Public Function GenerateScript(code As String) As IScript
Using provider As New VBCodeProvider()
Dim parameters As New CompilerParameters()
parameters.GenerateInMemory = True
parameters.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location)
Dim interfaceNamespace As String = GetType(IScript).Namespace
Dim codeArray() As String = New String() {"Imports " & interfaceNamespace & Environment.NewLine & code}
Dim results As CompilerResults = provider.CompileAssemblyFromSource(parameters, codeArray)
If results.Errors.HasErrors Then
Throw New Exception("Failed to compile script")
Else
Return CType(results.CompiledAssembly.CreateInstance("Script"), IScript)
End If
End Using
End Function
Now, you can call it like this:
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim builder As New StringBuilder()
builder.AppendLine("Public Class Script")
builder.AppendLine(" Implements IScript")
builder.AppendLine(" Public Property Variable1 As String Implements IScript.Variable1")
builder.AppendLine(" Public Sub DoWork() Implements IScript.DoWork")
builder.AppendLine(" Variable1 = ""Hello World""")
builder.AppendLine(" End Sub")
builder.AppendLine("End Class")
Dim script As IScript = GenerateScript(builder.ToString())
script.DoWork()
MessageBox.Show(script.Variable1) ' Displays "Hello World"
End Sub
Obviously, instead of building the code in a string builder, you could load it out of a text file, like this:
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim script As IScript = GenerateScript(File.ReadAllText("C:\script.txt")
script.DoWork()
MessageBox.Show(script.Variable1) ' Displays "Hello World"
End Sub
script.DoWork, it calls the Script.DoWork method that is defined in the string builder. In my example, all it does is set the value of the Variable1 property to "Hello World". But it could do anything you want--that's the beauty of it being a script :)DoWork method executes the code in the DoWork method, just as if it was defined locally in your own pre-compiled assembly. I just showed that IScript interface as an example. You could have as many methods and properties defined in that interface as you need. The Variable1 property was my attempt at demonstrating how to declare a variable, as you mentioned, with a script.