Dynamically invoke properties by string name using VB.NET

Question

I'm currently working on a project where a section of the code looks like this:

Select Case oReader.Name
    Case "NameExample1"
        Me.Elements.NameExample1.Value = oReader.ReadString
    ....
    Case "NameExampleN"
        Me.Elements.NameExampleN.Value = oReader.ReadString
    ....
End Select

It continues on for a while. The code is obviously verbose and it feels like it could be improved. Is there any way to dynamically invoke a property in VB.NET such that something like this can be done:

Dim sReadString As String = oReader.ReadString
Me.Elements.InvokeProperty(sReadString).Value = sReadString

Answer 1

You can use System.Reflection for this:

Me.GetType().GetProperty(oReader.Name).SetValue(Me, oReader.ReadString, nothing)

Answer 2

You are looking for reflection

http://www.vbdotnetheaven.com/UploadFile/rahul4_saxena/Reflection09122007031247AM/Reflection.aspx

Answer 3

Others have answered perfectly reasonably, but just in case this is a performance-sensitive piece of code, you might want to compile the reflective calls into delegates.

I've got a blog entry about turning MethodBase.Invoke into delegates. The code is in C#, but the same technique can be applied to VB.NET as well. To use this with properties, get the appropriate "setter" method with PropertyInfo.GetSetMethod and then build a delegate which invokes that. You could have a map from field name to "delegate to call to set the field".

Just to reiterate, this is only really necessary if it's in a performance-critical piece of code. Otherwise, you might still want to create a Dictionary<string, PropertyInfo> to avoid calling GetProperty many times, but the step to convert it into a delegate probably isn't worth worrying about.

Answer 4

I can't believe the other posters told you to use reflection. VB as a CallByName function that does exactly what you want.

Answer 5

Yeah... CallByName

Answer 6

Hi Jonathan Allen,

Thanx for your answer but there is no Interaction.CallByName in Silverlight