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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
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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
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typo: fieldInfo.GetValue({instance});
Marc
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and [dic] should have been [sic]... hmm: a typo in sic... vaguely ironic...
Two typos in one short post: time for coffee...
Marc
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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,stri ng>'
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
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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
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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
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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
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- date asked: Jun 22 '06
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