I am building web service in C# for a particular application, I have a XML definition of module. I have created a class called Field that holds the properties of all fields on a module. What I would like to do is create the field objects but name them dynamically then add them to a list of some sort. So when I reference them from the client it would be like this:
Module.Fields.MyDynamicName.FieldProperty
Is this possible to do? and could anyone point me in the right direction on how to do this.
Hope my question makes sense.
Basically you need to design for "deferred design", which means you do not know at compile time what the design is, but you still need to accommodate it.
There are probably a few ways but what I have done in the past is use a dictionary list of Key/Value pairs to store fields. Using serialization (I prefer Json) you can shove just about anything into a string and store it as the Value, then deserialize it when you need it.
Related
I have a predefined data format, which requires me to have an object like this:
settings:{
settingA:'someValueFromSql',
settingB:'someValueFromAD'
settingC:'someValueFromConfigFile',
settingD:'someValueFromReflection',
settingE:42,
...
}
This settings object is in fact a huge mess of data stitched together from many different sources, but this is how the data is expected by the frontend. I'd like to put the "get/process all data from one source" in a function each, and tape the object together in the end.
So I would have one object
sqlSettings:{
settingA:'someValueFromSql',
settingG:'someOtherValueFromSql',
...
}
returned by function a, and an object
adSettings:{
settingB:'someValueFromAD',
settingV:'someOtherValueFromAD',
...
}
returned by function b, and an object
settings includes adSettings, sqlSettings
where, with at most two simple steps, I can "join together" both objects into a flat third object.
Is this possible with fixed-size objects, without using a generic Dictionary, or am I barking up the wrong tree?
(I'm sure this question was already asked on SO, but I guess I don't find the right words)
It's not possible with a "normal" object, but you can do it with an ExpandoObject and the dynamic keyword. But you need at least .net 4.0
dynamic settings = new ExpandoObject();
//If you try to assign a property that doesn't exist, it is added to the object.
settings.SettingA="sfgd"
Anyway I discourage using this approach. why you don't want to use a IDictionary<string, object> or better a IDictionary<string, MyCustomSettingObject>
--------------------UPDATE---------------------
if the only thing that stops you from using a dictionary is the serialization you can implement the IXmlSerializable Interface and ouput the xml you like:
Proper way to implement IXmlSerializable?
If those partial setting objects have fixed size (meaning fixed number of properties), then you can definitely create a flat object with e.g. only properties to fit all the values in. Then to ease your work, you can try to use Automapper to map the partial objects to the "grouped" object.
http://automapper.codeplex.com/
Otherwise, you will have to stick with the dictionary.
I am tacking a large refactor of a project, and I had asked this question to confirm/understand the direction I should go in and I think I got the answer that I wanted, which is not to throw away years worth of code. So, now begins the challenge of refactoring the code. I've been reading Martine Fowler and Martin Feathers' books, and they have a lot of insight, but I am looking for advice on the ultimate goal of where I want the application to be.
So to reiterate the application a little bit, its a dynamic forms system, with lots of validation logic and data logic between the fields. The main record that gets inserted is the set of form fields that is on the page. Another part of it is 'Actions' that you can do for a person. These 'Actions' can differ client by client, and there are hundreds of 'Actions'. There is also talk that we can somehow make an engine that can eventually take on other similar areas, where a 'person' can be something else (such as student, or employee). So I want to build something very de-coupled. We have one codebase, but different DBs for different clients. The set of form fields on the page are dynamic, but the DB is not - it is translated into the specific DB table via stored procs. So, the generic set of fields are sent to the stored proc and the stored proc then decides what to do with the fields (figure out which table it needs to go to). These tables in fact are pretty static, meaning that they are not really dynamic, and there is a certain structure to it.
What I'm struggling specifically is how to setup a good way to do the dynamic form control page. It seems majority of the logic will be in code on the UI/aspx.cs page, because its loading controls onto the webpage. Is there some way I can do this, so it is done in a streamlined fashion, so the aspx.cs page isn't 5000 lines long? I have a 'FORM' object, and one of the properties is its' 'FIELDS'. So this object is loaded up in the business layer and the Data layer, but now on the fron end, it has to loop through the FIELDS and output the controls onto the page. Also, someway to be able to control the placement would be useful, too - not sure how do get that into this model....
Also, from another point of view - how can I 'really' get this into an object-oriented-structure? Because technically, they can create forms of anything. And those form fields can represent any object. So, for example, today they can create a set of form fields, that represent a 'person' - tomorrow they can create a set of form fields that represent a 'furniture'. How can I possibly translate this to to a person or a furniture object (or should I even be trying to?). And I don't really have controls over the form fields, because they can create whatever....
Any thought process would be really helpful - thanks!
How can I possibly translate this to to a person or a furniture object
(or should I even be trying to?)
If I understand you correctly, you probably shouldn't try to convert these fields to specific objects since the nature of your application is so dynamic. If the stored procedures are capable of figuring out which combination of fields belongs to which tables, then great.
If you can change the DB schema, I would suggest coming up with something much more dynamic. Rather than have a single table for each type of dynamic object, I would create the following schema:
Object {
ID
Name
... (clientID, etc.) ...
}
Property {
ID
ObjectID
Name
DBType (int, string, object-id, etc.)
FormType ( textbox, checkbox, etc.)
[FormValidationRegex] <== optional, could be used by field controls
Value
}
If you can't change the database schema, you can still apply the following to the old system using the stored procedures and fixed tables:
Then when you read in a specific object from the database, you can loop through each of the properties and get the form type and simple add the appropriate generic form type to the page:
foreach(Property p in Object.Properties)
{
switch(p.FormType)
{
case FormType.CheckBox:
PageForm.AddField(new CheckboxFormField(p.Name, p.Value));
break;
case FormType.Email:
PageForm.AddField(new EmailFormField(p.Name, p.Value));
break;
case FormType.etc:
...
break;
}
}
Of course, I threw in a PageForm object, as well as CheckboxFormField and EmailFormField objects. The PageForm object could simply be a placeholder, and the CheckboxFormField and EmailFormField could be UserControls or ServerControls.
I would not recommend trying to control placement. Just list off each field one by one vertically. This is becoming more and more popular anyway, even with static forms who's layout can be controlled completely. Most signup forms, for example, follow this convention.
I hope that helps. If I understood your question wrong, or if you'd like further explanations, let me know.
Not sure I understand the question. But there's two toolboxes suitable for writing generic code. It's generics, and it's reflection - typically in combination.
I don't think I really understand what you're trying to do, but a method using relfection to identify all the properties of an object might look like this:
using System.Reflection;
(...)
public void VisitProperties(object subject)
{
Type subjectType = subject.GetType();
foreach (PropertyInfo info in subjectType.GetProperties()
{
object value = info.GetValue(subject, null);
Console.WriteLine("The name of the property is " + info.Name);
Console.WriteLine("The value is " + value.ToString());
}
}
You can also check out an entry on my blog where I discuss using attributes on objects in conjunction with reflection. It's actually discussing how this can be utilized to write generic UI. Not exactly what you want, but at least the same principles could be used.
http://codepatrol.wordpress.com/2011/08/19/129/
This means that you could create your own custom attributes, or use those that already exists within the .NET framework already, to describe your types. Attributes to specify rules for validation, field label, even field placement could be used.
public class Person
{
[FieldLabel("First name")]
[ValidationRules(Rules.NotEmpty | Rules.OnlyCharacters)]
[FormColumn(1)]
[FormRow(1)]
public string FirstName{get;set;}
[FieldLabel("Last name")]
[ValidationRules(Rules.NotEmpty | Rules.OnlyCharacters)]
[FormColumn(2)]
[FormRow(1)]
public string LastName{get;set;}
}
Then you'd use the method described in my blog to identify these attributes and take the apropriate action - e.g. placing them in the proper row, giving the correct label, and so forth. I won't propose how to solve these things, but at least reflection is a great and simple tool to get descriptive information about an unknown type.
I found xml invaluable for this same situation. You can build an object graph in your code to represent the form easily enough. This object graph can again be loaded/saved from a db easily.
You can turn your object graph into xml & use xslt to generate the html for display. You now also have the benefit of customising this transform for differnetn clients/versions/etc. I also store the xml in the database for performance & to give me a publish function.
You need some specific code to deal with the incoming data, as you're going to be accessing the raw request post. You need to validate the incoming data against what you think you was shown. That stops people spoofing/meddling with your forms.
I hope that all makes sense.
I'm not really sure what tags should be on this sort of question so feel free to give me some suggestions if you think some others are more suited.
I have a dynamic object with an unknown number or properties on it, it's from a sort of dynamic self describing data model that lets the user build the data model at runtime. However because all of the fields holding relevant information to the user are in dynamic properties, it's difficult to determine what should be the human readable identifier, so it's left up to the administrator. (Don't think it matters but this is an ASP.NET MVC3 Application). To help during debugging I had started decorating some classes with DebuggerDisplayAttribute to make it easier to debug. This allow me to do things like
[DebuggerDisplay(#"\{Description = {Description}}")]
public class Group
to get a better picture of what a specific instance of an object is. And this sort of setup would be perfect but I can't seem to find the implementation of this flexibility. This is especially useful on my dynamic objects because the string value of the DebuggerDisplayAttribute is resolved by the .NET framework and I have implementations of TryGetMember on my base object class to handle the dynamic aspect. But this only makes it easier for development. So I've added a field on what part of my object is still strongly typed and called it Title, and I'd like to let the administer set the implementation using their own format, so to speak. So for example they might build out a very simplistic rental tracking system to show rentals and they might specify a format string along the lines of
"{MovieTitle} (Due: {DueDate})"
I would like that when they save the record to add some logic to first update the Title property by resolving the format string to substitute each place holder with the value of the appropriate property on the dynamic object. So this might resolve to a title of
"Inception (Due: May 21, 2011)", or a more realistic scenario of a format string of
"{LastName}, {FirstName}"
I don't want the user to have to update the title of a record when they change the first name field or the last name field. I fully realize this will likely use reflection but I'm hoping some one out there can give me some pointers or even a working example to handle complex format strings that could be a mix if literal text and placeholders.
I've not had much luck looking for an implementation on the net that will do what I want since I'm not really sure what keywords would give me the most relevant search results?
You need two things:
1) A syntax for formatting strings
You have already described a syntax where variables are surrounded by bracers, and if you want to use that you need to build a parser that can parse that. Perhaps you also want to add ways to specify say a date or a number format.
2) Rules for resolving variables
If there is a single context object you can use reflection and match variable names to properties but if your object model is more complex you can add conventions for searching say a hierarchy of objects.
If you are planning to base your model objects on dynamic chances are that you will find the Clay library on CodePlex interesting.
Right now, I'm currently serializing a class like this:
class Session
{
String setting1;
String setting2;
...etc... (other member variables)
List<SessionAction> actionsPerformed;
}
Where SessionAction is an interface that just has one method. All implementations of the SessionAction interface have various properties describing what that specific SessionAction does.
Currently, I serialize this to a file which can be loaded again using the default .Net binary serializer. Now, I want to serialize this to a template. This template will just be the List of SessionActions serialized to a file, but upon loading it back into memory at another time, I want some properties of these SessionActions to require input from the user (which I plan to dynamically generate GUI controls on the fly depending on the property type). Right now, I'm stuck on determining the best way to do this.
Is there some way I could flag some properties so that upon using reflection, I could determine which properties need input from user? Or what are my other options? Feel free to leave comments if anything isn't clear.
For info, I don't recommend using BinaryFormatter for anything that you are storing long-term; it is very brittle between versions. It is fine for short-lived messages where you know the same version will be used for serialization and deserialization.
I would recommend any of: XmlSerializer, DataContractSerializer (3.0), or for fast binary, protobuf-net; all of these are contract-based, so much more version tolerant.
Re the question; you could use things like Nullable<T> for value-types, and null for strings etc - and ask for input for those that are null? There are other routes involving things like the ShouldSerialize* pattern, but this might upset the serialization APIs.
If you know from start what properties will have that SessionAction, you must implement IDeserializationCallback and put to those props the attribute [NonSerialized]. When you implement the OnDeserialization method you get the new values from the user.
I have an application that reads a table from a database.
I issue an SQL query to get a result set, based on a unique string value I glean from the results, I use a case/switch statement to generate certain objects (they inherit TreeNode BTW). These created objects get shunted into a Dictionary object to be used later.
Whilst generating these objects I use some of the values from the result set to populate values in the object via the setters.
I query the Dictionary to return a particular object type and use it to populate a treeview. However it is not possible to populate 2 objects of the same type in a treeview from the Dictionary object (you get a runtime error - which escapes me at the moment, something to with referencing the same object). So what I have to do is use a memberwiseClone and implement IClonable to get around this.
Am I doing this right? Is there a better way - because I think this is causing my program to be real slow at this point. At the very least I think its a bit clunky - any advice from people who know more than me - greatly appreciated.
Is there a reason you are using the external dictionary? I would populate the tree directly as the data is queried.
If you do require the dictionary, you could set the .Tag property of the tree node to point to the data in your dictionary.
To add to #Brad, only populate the tree as needed. That means hooking into the expand event of the tree nodes. This is similar to how Windows Explorer functions when dealing with network shares.
There should be 1 TreeNode object per actual tree node in the tree - don't try to reuse the things. You may either associate them with your data using the Tag property (this is the recommended method), or you can subclass the TreeNode itself (this is the Java method, but used less in .NET).
(The use of cloning methods is usually a hint that you're either (a) doing something wrong, or (b) need to factor your domain model to separate mutable objects from immutable.)
have you considered using a Virtual Tree view which only loads the nodes the user actually wants to look at - i've had good success with the component from www.infralution.com