Hi,

How do get the Dictioanry object from FiedlInfo ?

my code :
fieldInfo = this.GetType().GetField("dictioanry1");
??Dictionary<string, string> dicTemp1 = (Dictionary<string, string>)fieldInfo;

Thanks
Wilson

The fieldInfo only knows about the type, not the instance: assuming that
fieldInfo isn't null (which suggests the field is public - is this really
correct?), then:

field.GetValue(this);

would return the value of the field in the current instance (since you are
using this.GetType() I assume this is what you want).

However, if "this" is correct (i.e. you really do mean the current
instance), then you can just use "dictioanry1" [dic] directly, without any
reflection?

dicTemp1 = dictioanry1;

Marc

typo: fieldInfo.GetValue({instance});

Marc

and [dic] should have been [sic]... hmm: a typo in sic... vaguely ironic...

Two typos in one short post: time for coffee...

Marc

Hello Marc,

Do you mean I need to change to :

fieldInfo = this.GetType().GetField("dictioanry1");
Dictionary<string, string> dicTemp1 = fieldInfo.GetValue(this);

Compiling error :
Cannot implicitly convert type 'object' to
'System.Collections.Generic.Dictionary<string,string>'

I need this because "dictionary1" is a string parameters only. I don't know
which dictionary until runtime.

Thanks
Wilson


"Marc Gravell" wrote:

> The fieldInfo only knows about the type, not the instance: assuming that
> fieldInfo isn't null (which suggests the field is public - is this really
> correct?), then:
>
> field.GetValue(this);
>
> would return the value of the field in the current instance (since you are
> using this.GetType() I assume this is what you want).
>
> However, if "this" is correct (i.e. you really do mean the current
> instance), then you can just use "dictioanry1" [dic] directly, without any
> reflection?
>
> dicTemp1 = dictioanry1;
>
> Marc
>
>
>

Yes; although you would need to cast

Dictionary<string, string> dicTemp1 = (Dictionary<string, string>)
fieldInfo.GetValue(this);

So yes: if you have multiple fields on the current instance called different
things, then this approach might work, i.e. if "dictionary1" is replaced
with a parameter; consider:

public class SomeClass {
private Dictionary<string, string> dictionary1, dictionary2, dictionary3,
dictionary4;
}

Then the code should work with any of "dictionary1"..."dictionary4" as
arguments to GetField (except that the fields are private, so probably won't
be found with GetField(blah)); however, the following approach would be more
efficient:
private Dictionary<string, string> GetDictionary(string fieldName) {
switch(fieldName) {
case "dictionary1": return dictionary1;
case "dictionary2": return dictionary2;
case "dictionary3": return dictionary3;
case "dictionary4": return dictionary4;
default: throw new ArgumentException("Dictionary " + fieldName + " not
recognised");
}

Additionally, this avoids the problems with the fields being private (which
needs a different overload to GetField); a tiny bit more effort, but much,
much quicker.

Marc

Oh, and you could also use an enum instead of a string as the argument; this
is quicker (switch on string compiles to a hashtable) and provides more
safety in that it is harder to call it with invalid arguments.

Marc

Thank you very much.

"Marc Gravell" wrote:

> Yes; although you would need to cast
>
> Dictionary<string, string> dicTemp1 = (Dictionary<string, string>)
> fieldInfo.GetValue(this);
>
> So yes: if you have multiple fields on the current instance called different
> things, then this approach might work, i.e. if "dictionary1" is replaced
> with a parameter; consider:
>
> public class SomeClass {
> private Dictionary<string, string> dictionary1, dictionary2, dictionary3,
> dictionary4;
> }
>
> Then the code should work with any of "dictionary1"..."dictionary4" as
> arguments to GetField (except that the fields are private, so probably won't
> be found with GetField(blah)); however, the following approach would be more
> efficient:
> private Dictionary<string, string> GetDictionary(string fieldName) {
> switch(fieldName) {
> case "dictionary1": return dictionary1;
> case "dictionary2": return dictionary2;
> case "dictionary3": return dictionary3;
> case "dictionary4": return dictionary4;
> default: throw new ArgumentException("Dictionary " + fieldName + " not
> recognised");
> }
>
> Additionally, this avoids the problems with the fields being private (which
> needs a different overload to GetField); a tiny bit more effort, but much,
> much quicker.
>
> Marc
>
>
>