Convert, e.g., string "System.Drawing.Colors.Red" into true datatype?

  • Thread starter Thread starter Ken Overton
  • Start date Start date
K

Ken Overton

Obviously the system does this for deserialization. So how can I do it
for arbitrary classes (not just enums)? Does this require generating a
temporary assembly and compiling it?

-- kov
 
Ken,
Obviously the system does this for deserialization. So how can I do it
for arbitrary classes (not just enums)?
Click to expand...

Type.GetType() or Assembly.GetType(). Since there can be multiple
types with the same name in different assemblies, you need to specify
which asembly to look in one way or another.

Does this require generating a temporary assembly and compiling it?
Click to expand...

No



Mattias
 
Mattias said:
Type.GetType() or Assembly.GetType(). Since there can be multiple
types with the same name in different assemblies, you need to specify
which asembly to look in one way or another.
Click to expand...

Sorry, I guess I'm a bit dense. I understand that
Type.GetType("System.Drawing.Color") will give me a Type object with all
the info about that class, but how can I use a Type object to actually
*create an instance* of that class? In my example above I suppose I
could get the PropertyInfo for the static property
System.Drawing.Colors.Red, but I'm not sure that is a generic solution
for all constant expressions of all types. I'm looking for a generic
solution to produce an instance of a constant given that constant
expression as a string and the type, like for example:

Class String Constant expression string
============ ======
"System.Drawing.Color" "Red"
"System.Int32" "0x0f"
"MyOwnClass.PiDouble" "3.14"
etc.

As far as I can see, if you want to call a method/property on an
instance via reflection, the instance has to already be created. I
suppose I could make my own factory to parse expressions and figure out
how to create them, it just seems like .NET already has that somewhere.
Either that or I have a poor understanding of the problem, which could
very well be.

-- kov
 
Nathan said:
Your best bet is to use a TypeConverter.
You'll need to apply the TypeConverterAttribute to your custom classes if
you want them to work with this approach.
Click to expand...

Thank you, Nathan, that looks like it's exactly what I was missing.

Cheers,

-- kov
 
Sorry, I guess I'm a bit dense. I understand that
Type.GetType("System.Drawing.Color") will give me a Type object with
all the info about that class, but how can I use a Type object to
actually *create an instance* of that class?
Click to expand...


Your best bet is to use a TypeConverter.
You'll need to apply the TypeConverterAttribute to your custom classes if
you want them to work with this approach.
The following code demonstrates a few different examples.


Type[] types = new Type[] {
typeof(Int32),
typeof(Color),
typeof(DayOfWeek),
typeof(DateTime),
typeof(MyClass)
};
string[] values = new string[] {
"13",
"Red",
"Saturday",
"2005-05-05",
"abc123"
};
for(int i = 0; i < types.Length; i++) {
object o = TypeDescriptor.GetConverter(
types).ConvertFrom(values);
Console.WriteLine("{0}\t{1}", o.GetType(), o);
}


Nathan
 
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