I want to be able to access property values in an object like a dictionary, using the name of the property as a key. I don't really care if the values are returned as objects, so Dictionary<string, object> is fine. This is the intended usage:
object person = new { Name: "Bob", Age: 45 };
IDictionary<string, object> lookup = new PropertyDictionary(person);
string name = (string)person["Name"];
person["Age"] = (int)person["Age"] + 1; // potentially editable
I was about to implement my own class for this, but then I started noticing classes like DynamicObject implement the IDictionary interface, which made think this was already being done for me somewhere.
What I want is similar to the functionality used by ASP.NET MVC that allows using anonymous types to set HTML tag attributes. I have a lot of classes that use dictionaries as data sources, but most of the time I should be able to pass in objects as well.
Since this is for a general-purpose library, I thought I would create a reusable class that simply decorated an object with the IDictionary interface. It will save me from creating an explosion of overloads.
I don't believe there is a built-in .Net type like this already in the .Net framework. It seems like you really want to create an object that behaves a lot like a Javascript object. If so then deriving from DynamicObject may be the right choice. It allows you to create an object which when wrapped with dynamic allows you to bind directly obj.Name or via the indexer obj["Name"].
public class PropertyBag : DynamicObject {
private object _source;
public PropertyBag(object source) {
_source = source;
}
public object GetProperty(string name) {
var type = _source.GetType();
var property = type.GetProperty(name, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
return property.GetValue(_source, null);
}
public override bool TryGetMember(GetMemberBinder binder, out object result) {
result = GetProperty(binder.Name);
return true;
}
public override bool TryGetIndex(GetIndexBinder binder, object[] indexes, out object result) {
result = GetProperty((string)indexes[0]);
return true;
}
}
You can use this to wrap any type and use both the indexer and name syntax to get the properties
var student = new Student() { FirstName = "John", LastName = "Doe" };
dynamic bag = new PropertyBag(student);
Console.WriteLine(bag["FirstName"]); // Prints: John
Console.WriteLine(bag.FirstName); // Prints: John
I have this extension method, probably the simplest it can get:
public static Dictionary<string, object> ToPropertyDictionary(this object obj)
{
var dictionary = new Dictionary<string, object>();
foreach (var propertyInfo in obj.GetType().GetProperties())
if (propertyInfo.CanRead && propertyInfo.GetIndexParameters().Length == 0)
dictionary[propertyInfo.Name] = propertyInfo.GetValue(obj, null);
return dictionary;
}
Now you can do:
object person = new { Name = "Bob", Age = 45 };
var lookup = person.ToPropertyDictionary();
string name = (string)lookup["Name"];
lookup["Age"] = (int)lookup["Age"] + 1; // indeed editable
Note:
that this dictionary is case-sensitive (you can trivially extend it passing the right StringComparer).
that it ignores indexers (which are also properties) but it's up to you to work on it.
that the method is not generic considering it doesn't help boxing because internally it calls obj.GetType, so it boxes anyway at that point.
that you get only the "readable" properties (otherwise you dont get the values held in it). Since you want it to be "writable" as well then you should use CanWrite flag as well.
dynamic keyword may be one option for you. it uses dynamic language runtime. At runtime, it tries to match the closest available type in the program. If it cant, then it converts the dynamic type to dictionay object, where key is the name of property and value is the value of property.
follow these links of MSDN:
Using dynamic keyword in C#
dynamic (C# Reference)
DLR Overview
usage of dynamic sample walkthough page
Related
Struggled to come up with a decent way to ask/title this question, but will try and illustrate it as best I can.
I am working with a data structure something like this:
public Foo
{
public Bar Bar {get;set;}
}
public Bar
{
public SubTypeA TypeA {get;set;}
public SubTypeB TypeB {get;set;}
...
}
public SubTypeA
{
public int Status {get;set;}
...
}
Note that I am unable to change the data structure for this.
There are many different types in the Bar class, which all have different properties within them, but common to all of them is the property of Status.
What I need to do, is given an object of type Foo, is record the statuses for every item in the Bar object within it. Not every SubType is going to have a value every time though, some could be null.
I can sort of manage it by using a recursive function like below to loop through all the properties. It isn't ideal though I don't think as the loop could get quite large as there could be a lot of properties on each SubType.
private void GetProperties(Type classType, object instance)
{
foreach (PropertyInfo property in classType.GetProperties())
{
object value = property.GetValue(instance, null);
if (value != null)
{
if (property.Name == "Status")
{
Record(classType, value);
}
GetProperties(property.PropertyType, value);
}
}
}
Is this about the only approach that there is for such a problem?
EDIT: Going by the answer given by Selman22, I have come up with another issue wherein I am trying to create an anonymous object based on the status and name of object.
var z = instance.GetType()
.GetProperties()
.Select(x => new
{
status = x.GetValue(instance).GetType().GetProperty("status").GetValue(x, null),
name = x.Name
})
.ToList();
This is throwing an error of Object does not match target type. when trying to retrieve the value. Is this possible in a 1 liner?
Type class contains GetProperty(string name, BindingFlags method) that you can use to retrieve specific property. Instead of looping through every property use this method.
http://msdn.microsoft.com/en-us/library/system.type.getproperty(v=vs.110).aspx
// Get Type object of MyClass.
Type myType=typeof(MyClass);
// Get the PropertyInfo by passing the property name and specifying the BindingFlags.
PropertyInfo myPropInfo = myType.GetProperty("MyProperty", BindingFlags.Public | BindingFlags.Instance);
You can get all Status properties using LINQ instead of recursion:
var barInstance = typeof(Foo).GetProperty("Bar").GetValue(fooInstance);
var statusProperties = barInstance.GetType()
.GetProperties()
.Select(x => x.GetValue(barInstance).GetType().GetProperty("Status"));
I want to write a generic function that takes an object and a series of properties of this object. Inside the function I would like to select a new anonymous object that is simply just those properties of the passed in object.
I want to do something like this:
public class SimpleClass
{
public DateTime ADate {get; set;}
public string StringHere {get; set;}
public int ANumber {get; set;}
}
var testObj = new SimpleClass();
// set values here on testObj properties
DoStuffHere(testObj, StringHere, ANumber);
I could pass in the properties as strings and then use reflection to get the properties from the passed in object, but I wanted to know if there was some way I could pass in the properties themselves so I could have intellisense and compile time checking to prevent bad property names. I would like my getNewClass function to take any type of object, and such, be generic.
Edit: I am not returning a new anonymous type. I think my function name was making it sound that way. I am going to be selecting a new anonymous type internally from a list of that specified testObj and generating a PDF from those properties.
Defining an anonymous type is actually very complicated, and trying to do it just with the names is somewhat challenging. Essentially what you want already exists, but in regular C# - so for a single object:
var obj = new { testObj.StringHere, testObj.ANumber };
Or for multiple objects:
var projection = from obj in sequence
select new { obj.StringHere, obj.ANumber };
That's about as succinct as you'll get. You could add a generic method that took a Func<,> of some kind, but it wouldn't be any cleaner than the above.
It isn't useful to have:
var obj = SomeMagicMethod(obj, "StringHere", "ANumber");
because SomeMagicMethod could only usefully return object - our obj variable would be largely unusable.
If you don't need to return the object from the method, then you could use either of:
SomeMagicMethod<T>(T value) {
...
}
...
SomeMagicMethod(new {testObj.StringHere, testObj.ANumber });
or:
SomeMagicMethod<TFrom, TTo>(TFrom value, Func<TFrom, TTo> selector)
{
TTo actualVal = selector(value);
...
}
...
SomeMagicMethod(testObj, x => new {x.StringHere, x.ANumber });
Personally, I think the first is easier - the func in the second is overkill.
You could also just use reflection...
SomeMagicMethod(object obj, params string[] names)
{
foreach(var name in names) {
object val = obj.GetType().GetProperty(name).GetValue(obj);
// ...
}
}
//...
SomeMagicMethod(testObj, "StringHere", "ANumber");
you can pass them as lambda:
GetNewClass (testObj, ()=>StringHere, ()=> ANumber);
and have a signature for GetNewClass like
void GetNewClass (object, Expression<Func<object>> expr0, Expression<Func<object>> expr1);
You can then get the property quite easily.
You can use Linq expressions for that.
(note: it's possible you need to modify a few things in the snippet below, this is of the top of my hat):
public void getNewClass(Object testObj, params MemberExpression Fields[])
{
foreach(MemberExpression field in Fields)
{
// Get the name
var name = field.Member.Name;
// get the value
var member= Expression.Convert(field, typeof(object));
var lambda= Expression.Lambda<Func<object>>(member);
var fnc= lambda.Compile();
var value = fnc();
}
}
This snippet show how to get the name of the property and the value. It can be called like this:
getClass(someObj, obj => obj.SomeProperty, obj.SomeOtherProperty);
I have a "settings" class, which has some properties for usability and to restrict set accessor. It seems easy while i had within ten items, but then their count was increased. I need some way to create these properties automatically, something like that:
foreach(var property in SettingsList)
{
_settings.AddAutoProperty(property);
}
It may have deal with reflection, but i can't get to efficient solution.
The properties definition:
public bool cbNextExcCount
{
get { return (bool)this.GetValueById("cbNextExcCount"); }
}
public bool cbSaveOnChangeExc
{
get { return (bool)this.GetValueById("cbSaveOnChangeExc"); }
}
public bool cbAutoIncrement
{
get { return (bool)this.GetValueById("cbAutoIncrement"); }
}
public bool cbRememberOnExit
{
get { return (bool)this.GetValueById("cbRememberOnExit"); }
}
...etc.
UPDATE
To summ up, i wrote the next code:
public IDictionary<string, object> Properties = new ExpandoObject();
private List<string> SettingsList = new List<string>
{
"cbNextExcCount",
"cbSaveOnChangeExc",
"cbAutoIncrement",
"cbRememberOnExit"
};
public void CreateProperties()
{
foreach (string SettingName in SettingsList)
{
Properties.Add(SettingName, () => this.GetValueById(SettingName));
}
}
But i have an error on () => this.GetValueById("cbNextExcCount")):
argument type 'lambda expression' is not assignable to parameter type 'object'.
I can store Func<bool>, but settings may have other type than bool and if i use Func, it's get a bit more complicate to call.
You can't create auto-properties, but you can use an ExpandoObject.
I'm not sure if this is what you're looking for, because using expandos means using duck typing (i.e. dynamic programming).
ExpandoObject sample:
dynamic expando = new ExpandoObject();
expando.PropertyA = "Hello";
expando.PropertyB = "world!";
An interesting thing about expandos is that ExpandoObject implements IDictionary<string, object>, meaning that you can upcast any expando to this type and iterate over its added properties, which could be great for storing run-time created settings.
UPDATE
I was thinking more about a good solution and if SettingList is a custom class developed by yourself, maybe you can add a property called Custom to SettingList and add there settings that aren't added during design-time.
UPDATE 2
In your case, instead of storing the actual value of something, you could add Func<bool> to ExpandoObject's run-time settings:
IDictionary<string, object> settings = new ExpandoObject();
settings.Add("cbNextExcCount", () => this.GetValueById("cbNextExcCount"));
Actually, I don't know this scope in your code sample, but change this to anything that could be an instance of SettingList or whatever.
Once you've added run-time settings, you can type settings variable to dynamic typing in order to access properties like this:
dynamic allSettings = (dynamic)settings;
bool cbNextExcCount = allSettings.cbNextExcCount();
You can consider Expando Objects in System.Dynamic namespace. This article can be a good start.
I want to create a property of a class, and set the name of that property using a variable value.
E.g.
string resultValue = "stack";
MyClass myclass = new MyClass();
myclass.resultValue = "overflow";
Now here in this case, stack is the property name and "overflow" is the value of the stack property.
Please tell how is it possible.
Thanks in advance.
You could use Reflection. For example:
string name = "stack";
string value = "overflow";
PropertyInfo pi = typeof(MyClass).GetProperty(name);
MyClass instance = new MyClass();
pi.SetValue(instance, value, null);
// at this stage instance.stack equals to "overflow"
This obviously assumes that MyClass has a public property stack with a public setter:
public class MyClass
{
public string stack { get; set; }
}
You should use Reflection for this
MyClass myclass = new MyClass();
Type type = typeof(MyClass);
PropertyInfo property = type.GetProperty("stack");
property.SetValue(myclass, "overflow", null);
I think that the Dynamic Source Code Generation and Compilation section on MSDN should contain the information you need.
The .NET Framework includes a mechanism called the Code Document
Object Model (CodeDOM) that enables developers of programs that emit
source code to generate source code in multiple programming languages
at run time, based on a single model that represents the code to
render.
I think that you could also get this done using Reflection.
Maybe you should take a look at DynamicObject. With this you can create properties at runtime by simply assigning a value. An example can also be found at the MSDN article.
Have at look at Mark Gravell's FastMember
It allows you to set properties in a dynamic manner.
// obj could be static or DLR
var wrapped = ObjectAccessor.Create(obj);
string propName = // something known only at runtime
FastMember Blog Post
I can't imagine why you want to generate property on your class, but consider other ways. E.g. using Dictionary:
class MyClass
{
Dictionary<string, object> _values = new Dictionary<string, object>();
public object this[string name]
{
get
{
if (!_values.ContainsKey(name))
throw new ArgumentException(name);
return _values[name];
}
set
{
if (!_values.ContainsKey(name))
{
_values.Add(name, value);
return;
}
_values[name] = value;
}
}
}
Usage:
MyClass myClass = new MyClass();
myClass["stack"] = "overflow";
Console.WriteLine(myClass["stack"]);
As far as I know, is this not possible. You can try using a dictionary.
Suppose I have Dictionary like this:
Dictionary<string, string> values = new Dictionary<string, string>()
{
{ "Name" , "John Smith"},
{ "Age", "34"}
};
Now I want to create type from that dictionary and initialize it with values in run-time so that I was able to access it's properties with reflection.
For this example I want object with property Name equals to "Jon Smith" and Age equals to 34.
Edit:
I need this to compare two objects with semantic comparison library such as TestApi. First object created by other code that has strong type
class Person
{
public string Name {get; set;}
public int Age { get; set;}
}
and other I need to create from other source like xml file (but not necessary). Types that would be compared are known only in run-time.
If you're using C# 4 you could use dynamic and ExpandoObject for this - it's not actually creating a new type, but it's close enough in some cases:
IDictionary<string, object> foo = new ExpandoObject();
foreach (var pair in values)
{
foo[pair.Key] = pair.Value;
}
dynamic d = foo;
string name = d.Name;
string age = d.Age; // This will still be a string, not an int
EDIT: I missed that you wanted to access the data with reflection. Using reflection is a way of effectively treating the type like a map - and you've already got it in that form. Why not just access the dictionary directly? The only benefit would be if you wanted to be able to use some types with reflection, and some with a dictionary. In that case I'd create a general-purpose interface with two implementations - one of which got values from a dictionary, and one of which used reflection. That's going to be a lot easier than creating a type on the fly (which is possible, but not a lot of fun).