step through a struct using foreach

[titan nyquist]

Can I step through a struct using foreach? I want a method that steps
through a struct, and prints out the name/value of each member. Can
it be done?

The error I get when trying this is: "foreach statement cannot
operate on variables of type '...' because '...' does not contain a
public definition for 'GetEnumerator' . And it points me to

http://msdn2.microsoft.com/en-us/library/t51esaeb(vs.80).aspx

I guess this is the answer, but it is over my head at this moment.

[Marc Gravell]

Re: step through a struct using foreach

What do you mean, "steps through a struct"? If you mean the
sub-properties, then something like

foreach(Propert yDescriptor property in
TypeDescriptor. GetProperties(m yValue)) {
Debug.WriteLine (property.GetVa lue(myValue),
property.Name);
}

may suffice...

Marc

[titan nyquist]

Re: step through a struct using foreach

Marc,

Here's example code (that does not work) of what I was trying to do:

namespace DisplayStructCo ntentsTest
{
class Program
{

struct Employee
{
public string name;
public int age;
public string location;
};

static void Main(string[] args)
{
Employee employee;

employee.name = "Jim Smith";
employee.age = 35;
employee.locati on = "California ";

foreach (object obj in employee)
{
Console.WriteLi ne(obj + " = " + obj.ToString()) ;

// Output I wish for:
//
// name = Jim Smith
// age = 35
// location = California
}


}
}
}

[titan nyquist]

Re: step through a struct using foreach

The point is, if I modify the struct, I want the code to automatically
handle the new structure. For example, if I add a "birthdate" field,
the code should (without modification) display the birthdate.

[Marc Gravell]

Re: step through a struct using foreach

Exposing fields forces you to use reflection; very similar to the
component model code:

foreach (FieldInfo fi in employee.GetTyp e().GetFields() ) {
Console.WriteLi ne(fi.Name + " = " +
Convert.ToStrin g(fi.GetValue(e mployee)));
}

But!! I can't tell you how to code, but you are a: using public
fields, and b: using mutable structs. Neither of these is particularly
good practice in .Net. Please note that CLR structs are very different
to C[++] structs; they are not the same, and perhaps it was
unfortunate to call them structs in C#. What you have feels more like
a class. The public fields are marginally less critical, but prevent
you from doing any find of validation / notification, or changing the
model. I strongly advise using .Net the way it is intended, i.e.
(short version):

class Employee {
private string name, location;
private int age;
public string Name { get { return name; } set { name =
value; } }
public string Location { get { return location; } set {
location = value; } }
public int Age { get { return age; } set { age =
value; } }
};

This obeys a lot more CLR conventions, and will work more as expected
in collections etc.

Marc

[Marc Gravell]

Re: step through a struct using foreach

Don't worry... we get it ;-p See other post.

However; this precisely illustrates my point re properties. When you
add the "birthdate" , you might want to cease having "age" as a field,
and start using a calculated "get", i.e. using the offset from
DateTime.Now when the "get" is called.

Marc

[Tom Porterfield]

Re: step through a struct using foreach

titan nyquist wrote:

The point is, if I modify the struct, I want the code to automatically
handle the new structure. For example, if I add a "birthdate" field,
the code should (without modification) display the birthdate.

The following should do it:

Employee employee;

employee.name = "Jim Smith";
employee.age = 35;
employee.locati on = "California ";

Type t = employee.GetTyp e();
System.Reflecti on.FieldInfo [] fields =
t.GetFields(Sys tem.Reflection. BindingFlags.In stance|System.R eflection.Bindi ngFlags.Public) ;

foreach (System.Reflect ion.FieldInfo field in fields)
{
Console.WriteLi ne(field.Name + " = " + field.GetValue( employee));
}
--
Tom Porterfield