Create A TO_DATE Function For Use In SQLServer 2005

Hi ,

I 'm working with visual studio 2005 and I have created an SQLServer Project.
I'm using the CLR functionality which comes with SQLserver 2005. This means that I can write VB.nEt code and use it inside Sqlserver 2005.So far so good.
I am now inside the .NET
I have created a Function(must remind you that I have created an SQLserver Project) which takes two string arguments. The date value in a string format and the string format.

In Our case the function returns a string.It will return a datetime although.
So we have

Dim Datetime_Val As DateTime = Nothing
Dim Date_Val As Date = Nothing
Dim StrTemp As String = ""
Dim StrDateTemp As String = Nothing
Dim StrTimeTemp As String = Nothing
Dim ls_return As String = Nothing
Dim lindexof As Integer
Dim Counter As Integer = 0

lindexof = 0
Select Case StrFormat
Case "DD-MM-YYYY HH24:MIS"
For Counter = 1 To 2
lindexof = StrDate.IndexOf("-", lindexof + 1)
Next
lindexof += 5

StrDateTemp = StrDate.Substring(0, lindexof).Trim
StrTimeTemp = StrDate.Substring(StrDateTemp.Length, StrDate.Length - StrDateTemp.Length).Trim
ls_return = StrDateTemp & " " & StrTimeTemp

End Select

The above is a simple code. As you can see I'm trying to convert the TO_DATE function ,which work with ORACLE, to make it work with SQLServer 2005.
I've been trying unsuccessfully to combine the variables StrDateTemp and StrTimeTemp into a datetime value. I used the following code but nothing

Datetime_Val = CDate(StrDateTemp & " " & StrTimeTemp)
Didn't work

Datetime_Val = Convert.ToDateTime(StrDateTemp & " " & StrTimeTemp)
Didn't work

Datetime_Val = DateTime.Parse(StrDateTemp & " " & StrTimeTemp)
Didn't work

Inside SQlServer I used this SQL statement

Select dbo.TO_DATE('31-12-1990 00:26:46','DD-MM-YYYY HH24:MIS')

But I am receiveing an error. I want to avoid changing all of my applications with a specific format.This sql statement without the dbo prefix I'm using in Oracle. I want to keep the format of the SQL and let VB.NET do the parsing for me. It is easier for me to put in my SQLs the dbo infront rather changing the complete SQL.
I have two questions . How am I going to create a TO_DATE function which Oracle uses and write something similar in SQLserver ?
And If I cannot do that how am I going to get the database 's datetime format and create with VB.NET the Datetime value from the two variables ?

My problem I believe is quite complex. I would be mostly appreciated if you could help me on this.

Thank you