.net - Assign Value To String?

Consider following code:

Dim S1 As String = "a"
'this is the string in a file
Dim StringFromFile As String = "S1=hello"

[code]....

how to assign value to S1?I have declared a string named S1. Now I want to assign new value to S1. The new string value is stored in a file using following format: [variable name][= as separator][string value]. How do I assign the value to S1 after retrieving the string variable name and value that stored in a file?

NOTE:

temp(0) = "S1"
temp(1) = "hello"

It should be noted that the string with the data comes from a file that may change from time to time! When the file changes, I want the variables to change as well.

Further clarification I need a piece of code that when processing a string like this "S1=hello", the code will first find a declared variable (i.e. S1), and then assign the S1 variable with "hello" string. The "=" just acted as separator for variable name and variable value.

UPDATE:

My attempt to use Mathias Lykkegaard Lorenzen's EDIT 2 example but failed with "NullReferenceException" on this line "Field.SetValue(Me, VariableValue)". Please help me fix the problem. Following is my code based on Mathias Lykkegaard Lorenzen's EDIT 2 example:

Public Sub Ask()
Try
Dim S1 As String = "a"
Dim StringFromFile As String = "S1=hello"

[code]....