Dynamic code execution: String -> Runtime code VB.net - vb.net

Question

I'm trying to execute some code inside a string in runtime. I.E.
Dim code As String = "IIf(1 = 2, True, False)"
How do i run the code inside code string ?

Answer 1

As #ElektroStudios said - the proper way to do this is to use the CodeDom compiler, but this is a bit overkill for something as simple as this.
You can sort of cheat and harness the power of a DataColumn Expression
So for example:
Dim formula = "IIF(Condition = 'Yes', 'Go', 'Stop')"
Dim value As String = "Yes"
Dim result As String
'add a columns to hold the value
Dim colStatus As New DataColumn
With colStatus
.DataType = System.Type.GetType("System.String")
.ColumnName = "Condition"
End With
'add a column to compute the expression
Dim colExp As New DataColumn
With colExp
.DataType = System.Type.GetType("System.String")
.ColumnName = "Expression"
.Expression = formula
End With
'create a table and add the columns
Dim dt As New DataTable
With dt.Columns
.Add(colStatus)
.Add(colExp)
End With
'now add a row and set the condition to the value we have
Dim row As DataRow = dt.NewRow
row.SetField(Of String)("Condition", value)
dt.Rows.Add(row)
'now read back the computed value based on the expression being evaluated
result = row.Field(Of String)("Expression")
MessageBox.Show(result)
You could wrap all this up into a more generic function like this:
Public Function EvaluateExpression(Of T, K)(input As T, formula As String) As K
'add a columns to hold the value
Dim colStatus As New DataColumn
With colStatus
.DataType = GetType(T)
.ColumnName = "Condition"
End With
'add a column to compute the expression
Dim colExp As New DataColumn
With colExp
.DataType = GetType(K)
.ColumnName = "Expression"
.Expression = formula
End With
'create a table and add the columns
Dim dt As New DataTable
With dt.Columns
.Add(colStatus)
.Add(colExp)
End With
'now add a row and set the condition to the value we have
Dim row As DataRow = dt.NewRow
row.SetField(Of T)("Condition", input)
dt.Rows.Add(row)
'now read back the computed value based on the expression being evaluated
Return row.Field(Of K)("Expression")
End Function
So then you can call it like this:
Dim result = EvaluateExpression(Of Integer, Boolean)(1, "IIF(Condition = 1, True, False)")