Compile and Run VB.NET Code using the CodeDom

Imports System.Text



Public Class frmMain


    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click

        Dim oRetVal As Object = CompileAndRunCode(Me.RichTextBox1.Text)

        MsgBox(oRetVal)

    End Sub


    Private Function GenerateCannedRoutine() As StringBuilder
        Dim oRetSB As New StringBuilder

        ' Grab a variable from somewhere....
        Dim sText As String = "July 30, 2006"

        oRetSB.Append("If Date.Parse(""" & sText & """) < System.DateTime.Now() Then " & vbCrLf)
        oRetSB.Append(" Return ""OLD"" " & vbCrLf)
        oRetSB.Append("Else " & vbCrLf)
        oRetSB.Append(" Return ""NEW"" " & vbCrLf)
        oRetSB.Append("End If " & vbCrLf)

        Return oRetSB
    End Function

    Public Function CompileAndRunCode(ByVal VBCodeToExecute As String) As Object

        Dim sReturn_DataType As String
        Dim sReturn_Value As String = ""
        Try

            ' Instance our CodeDom wrapper
            Dim ep As New cVBEvalProvider

            ' Compile and run
            Dim objResult As Object = ep.Eval(VBCodeToExecute)
            If ep.CompilerErrors.Count <> 0 Then
                Diagnostics.Debug.WriteLine("CompileAndRunCode: Compile Error Count = " & ep.CompilerErrors.Count)
                Diagnostics.Debug.WriteLine(ep.CompilerErrors.Item(0))
                Return "ERROR" ' Forget it
            End If
            Dim t As Type = objResult.GetType()
            If t.ToString() = "System.String" Then
                sReturn_DataType = t.ToString
                sReturn_Value = Convert.ToString(objResult)
            Else
                ' Some other type of data - not really handled at 
                ' this point. rwd
                'ToDo: Add handlers for other data return types, if needed

                ' Here is an example to handle a dataset...
                'Dim ds As DataSet = DirectCast(objResult, DataSet)
                'DataGrid1.Visible = True
                'TextBox2.Visible = False
                'DataGrid1.DataSource = ds.Tables(0)
            End If

        Catch ex As Exception
            Dim sErrMsg As String
            sErrMsg = String.Format("{0}", ex.Message)
            ' Do Nothing - This is just a negative case
            ' This outcome is expected in late interpreting
            ' I suppose what I am saying is: Don't stop my program because the script writer can't write
            ' script very well.  To be fair, we could log this somewhere and notify somebody.
        End Try

        Return sReturn_Value

    End Function

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        ' Build our code fragment 
        Dim sCode As System.Text.StringBuilder
        sCode = GenerateCannedRoutine()
        Me.RichTextBox1.Text = sCode.ToString

    End Sub
End Class