Hi! I edited your code to fit it in a smaller space for easier viewing,
but it shouldn't change the concepts.
Shmuel Cohen wrote:
public class MyEnums {
public enum DATA_ITEM {FIRST,SECOND,T HIRD,FOURTH,FIF TH};
}
public class TheData { public double a, b, c; }
public class Utility {
private static double adder (TheData data, FIELD fld) {
double val = 0.0;
val += data.fld;
}
public static double SUM_DATA (TheData mdc, MyEnums.DATA_IT EM di) {
switch (di) {
case MyEnums.DATA_IT EM.FIRST:
return adder (mdc, FIELD a);
case MyEnums.DATA_IT EM.SECOND:
return adder (mdc, FIELD b);
}
return 0.0;
}
}
The simplest way to accomplish this is to use reflection. Given a string
name, you can retrieve the field with that name and type FieldType from
object obj with the following expression:
(FieldType)obj. GetType().GetFi eld(name).GetVa lue(obj)
Here it is in your example:
public class Utility {
private static double adder (TheData data, string fld) {
double val = 0.0;
val += (double)data.Ge tType().GetFiel d(fld).GetValue (data);
return val;
}
public static double SUM_DATA(TheDat a mdc, MyEnums.DATA_IT EM di) {
switch (di) {
case MyEnums.DATA_IT EM.FIRST:
return adder (mdc, "a");
case MyEnums.DATA_IT EM.SECOND:
return adder (mdc, "b");
}
return 0.0;
}
}
If you find the syntax annoyingly verbose, you may find the following
class I whipped up helpful:
public class FieldReflector
{
private Object _obj;
public FieldReflector( Object obj)
{
_obj = obj;
}
public Object this[string name]
{
get
{
return _obj.GetType(). GetField(name). GetValue(_obj);
}
set
{
_obj.GetType(). GetField(name). SetValue(_obj, value);
}
}
}
Now you can simply do this:
private static double adder (TheData data, string fld)
{
FieldReflector datafr = new FieldReflector( data);
double val = 0.0;
val += (double)datafr[fld];
return val;
}
However, reflection can have a significant performance cost, so be
careful not to use it extensively in performance-critical paths.
Instead, you may wish to simply use an array of instance variables and
access them using properties:
public class TheData
{
public double[] fields = new double[3];
public double a
{
get { return fields[0]; }
set { fields[0] = value; }
}
public double b
{
get { return fields[1]; }
set { fields[1] = value; }
}
public double c
{
get { return fields[2]; }
set { fields[2] = value; }
}
public enum FieldNames { A, B, C }
}
public class Utility
{
private static double adder (TheData data, TheData.FieldNa mes fld)
{
double val = 0.0;
val += (double)data.fi elds[(int)fld];
return val;
}
}
Please ask if any of this is unclear to you. I hope this helps.
--
Derrick Coetzee, Microsoft Speech Server developer
This posting is provided "AS IS" with no warranties, and confers no
rights. Use of included code samples are subject to the terms
specified at
http://www.microsoft.com/info/cpyright.htm 
