[Silverlight entry series] Validation: Is inotifypropertychanged and inotifydataerrorinfo implemented in model or viewmodel?

Validation is divided into the following types:

1. Type and length: for example, \ D {} can contain up to three digits, which must be numbers.
2. Range: for example, a-Za-Z, greater than 100 and less than 200
3. Business logic: Special, such as checking that a database name is unique (the backend service must be called) or other business logic.

In silverlight4, validation implements the inotifypropertychanged and inotifydataerrorinfo interfaces, which can be either placed in the model or viewmodel. (Do not implement both ). If your validation rules are relatively simple, for example, the first two types of rules above, it is more appropriate to put them in the model. However, if your validation rules are complex and special, you need to use business logic to call backend services asynchronously, and so on, it is more appropriate to put them in viewmodel.

The inotifydataerrorinfo interface is added to silverlight4.0:

 
1:NamespaceSystem. componentmodel
 
 
2 :{
 
 
3:Public InterfaceInotifydataerrorinfo
 
 
4 :{
 
5:BoolHaserrors {Get;}
 
 
6:EventEventhandler <dataerrorschangedeventargs> errorschanged;
 
 
7: ienumerable geterrors (StringPropertyname );
 
 
8 :}
 
 
9 :}
 
 
There is also the inotifypropertychanged interface:
 
 
1:NamespaceSystem. componentmodel
 
 
2 :{
 
 
3:Public InterfaceInotifypropertychanged
 
 
4 :{
 
 
5:EventPropertychangedeventhandler propertychanged;
 
 
6 :}
 
7 :}
 
 
Here is an example:
 
 
1:Public Abstract ClassMyxxx: inotifypropertychanged, inotifydataerrorinfo
 
 
2 :{
 
 
3:PrivateErrorscontainer <validationresult> errorscontainer;
 
 
4:
 
 
5:/// <Summary>
 
 
6:/// Initializes a new instance of the <see CREF = "domainobject"/> class.
 
 
7:/// </Summary>
 
 
8:ProtectedMyxxx ()
 
 
9 :{
 
 
10 :}
 
11:
 
 
12:/// <Summary>
 
 
13:/// Event raised when a property value changes.
 
 
14:/// </Summary>
 
 
15:/// <Seealso CREF = "inotifypropertychanged"/>
 
 
16:Public EventPropertychangedeventhandler propertychanged;
 
 
17:
 
 
18:/// <Summary>
 
 
19:/// Event raised when the validation status changes.
 
 
20:/// </Summary>
 
21:/// <Seealso CREF = "inotifydataerrorinfo"/>
 
 
22:Public EventEventhandler <dataerrorschangedeventargs> errorschanged;
 
 
23:
 
 
24:/// <Summary>
 
 
25:/// Gets the error status.
 
 
26:/// </Summary>
 
 
27:/// <Seealso CREF = "inotifydataerrorinfo"/>
 
 
28:Public BoolHaserrors
 
 
29 :{
 
30:Get{Return This. Errorscontainer. haserrors ;}
 
 
31 :}
 
 
32:
 
 
33:/// <Summary>
 
 
34:/// Gets the container for errors in the properties of the domain object.
 
 
35:/// </Summary>
 
 
36:ProtectedErrorscontainer <validationresult> errorscontainer
 
 
37 :{
 
 
38:Get
 
 
39 :{
 
40:If(This. Errorscontainer =Null)
 
 
41 :{
 
 
42:This. Errorscontainer =
 
 
43:NewErrorscontainer <validationresult> (Pn =>This. Raiseerrorschanged (PN ));
 
 
44 :}
 
 
45:
 
 
46:Return This. Errorscontainer;
 
 
47 :}
 
 
48 :}
 
 
49:
 
 
50:/// <Summary>
 
51:/// Returns the Errors for <paramref name = "propertyname"/>.
 
 
52:/// </Summary>
 
 
53:/// <Param name = "propertyname"> the name of the property for which the errors are requested. </param>
 
 
54:/// <Returns> An enumerable with the errors. </returns>
 
 
55:/// <Seealso CREF = "inotifydataerrorinfo"/>
 
 
56:PublicIenumerable geterrors (StringPropertyname)
 
 
57 :{
 
58:Return This. Errorscontainer. geterrors (propertyname );
 
 
59 :}
 
 
60:
 
 
61:/// <Summary>
 
 
62:/// Raises the <see CREF = "propertychanged"/> event.
 
 
63:/// </Summary>
 
 
64:/// <Param name = "propertyname"> the name of the changed property. </param>
 
 
65: [suppressmessage ("Microsoft. Design","Ca1030: useeventswhereappropriate", Justification ="Method supports event.")]
 
66:Protected VoidRaisepropertychanged (StringPropertyname)
 
 
67 :{
 
 
68:This. Onpropertychanged (NewPropertychangedeventargs (propertyname ));
 
 
69 :}
 
 
70:
 
 
71:/// <Summary>
 
 
72:/// Raises the <see CREF = "propertychanged"/> event.
 
 
73:/// </Summary>
 
 
74:/// <Param name = "E"> the argument for the event. </param>
 
75:Protected Virtual VoidOnpropertychanged (propertychangedeventargs E)
 
 
76 :{
 
 
77: var handler =This. Propertychanged;
 
 
78:If(Handler! =Null)
 
 
79 :{
 
 
80: handler (This, E );
 
 
81 :}
 
 
82 :}
 
 
83:
 
 
84:/// <Summary>
 
85:/// Validates <paramref name = "value"/> as the value for the property named <paramref name = "propertyname"/>.
 
 
86:/// </Summary>
 
 
87:/// <Param name = "propertyname"> The Name Of The property. </param>
 
 
88:/// <Param name = "value"> the value for the property. </param>
 
 
89:Protected VoidValidateproperty (StringPropertyname,Object Value)
 
 
90 :{
 
91:If(String. Isnullorempty (propertyname ))
 
 
92 :{
 
 
93:Throw NewArgumentnullexception ("Propertyname");
 
 
94 :}
 
 
95:
 
 
96:This. Validateproperty (NewValidationcontext (This,Null,Null) {Membername = propertyname },Value);
 
 
97 :}
 
 
98:
 
 
99:/// <Summary>
 
100:/// Validates <paramref name = "value"/> as the value for the property specified
 
 
101:/// <Paramref name = "validationcontext"/> using data annotations validation attributes.
 
 
102:/// </Summary>
 
 
103:/// <Param name = "validationcontext"> the context for the validation. </param>
 
 
104:/// <Param name = "value"> the value for the property. </param>
 
105:Protected Virtual VoidValidateproperty (validationcontext,Object Value)
 
 
106 :{
 
 
107:If(Validationcontext =Null)
 
 
108 :{
 
 
109:Throw NewArgumentnullexception ("Validationcontext");
 
 
110 :}
 
 
111:
 
 
112: List <validationresult> validationresults =NewList <validationresult> ();
 
113: validator. tryvalidateproperty (Value, Validationcontext, validationresults );
 
 
114:
 
 
115:This. Errorscontainer. seterrors (validationcontext. membername, validationresults );
 
 
116 :}
 
 
117:
 
 
118:/// <Summary>
 
 
119:/// Raises the <see CREF = "errorschanged"/> event.
 
 
120:/// </Summary>
 
 
121:/// <Param name = "propertyname"> the name of the property which changed its error status. </param>
 
122: [suppressmessage ("Microsoft. Design","Ca1030: useeventswhereappropriate", Justification ="Method supports event.")]
 
 
123:Protected VoidRaiseerrorschanged (StringPropertyname)
 
 
124 :{
 
 
125:This. Onerrorschanged (NewDataerrorschangedeventargs (propertyname ));
 
 
126 :}
 
 
127:
 
 
128:/// <Summary>
 
 
129:/// Raises the <see CREF = "errorschanged"/> event.
 
130:/// </Summary>
 
 
131:/// <Param name = "E"> the argument for the event. </param>
 
 
132:Protected Virtual VoidOnerrorschanged (dataerrorschangedeventargs E)
 
 
133 :{
 
 
134: var handler =This. Errorschanged;
 
 
135:If(Handler! =Null)
 
 
136 :{
 
 
137: handler (This, E );
 
 
138 :}
 
 
139 :}
 
 
140 :}