input validation before saving data into the database in wpf c# using mvvm

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i am fresher to WPf concept. i want to do a project based on "employement registration".this work needs the input fields name,age,depatrment,designation,salary.these details should be saved in sql database only after the validation. the name field should only contains alphabets and age field should contain only numbers.can we use mvvm to this??how can i implement this using mvvm concept?

Posted 17-Dec-12 18:53pm

Anmerin

Updated 17-Dec-12 22:32pm

v3

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Oleksandr Kulchytskyi · Accepted Answer · 2012-12-18T03:47:00

Solution 1

Hi , check here.
Obviously for simplicity your domain model -> Employee needs to inherit

IDataErrorInfo

then implement in this domain model property (which is a declared in this interface):

C#

public string this[string columnName]

and internally check your fields there , in case of inproper data for each property notify about it in format of string data.
Also you can check here:
idataerrorinfo-for-validation-in-mvvm-with-silverlight-and-wpf/[^]

Posted 18-Dec-12 3:47am

Oleksandr Kulchytskyi

Updated 18-Dec-12 3:48am

v2

Comments

Anmerin 18-Dec-12 22:33pm

thanks for ur response.i cant understand the mvvm model.i came to know that there is some divisons like view,model,model view and we have to create separate classes for each one except the view which is our xaml part.and each class is having some functionality like properties should be implemented in one class all the actions should be implemented in another class which also uses inotify proerty.will u pls give me brief skeleton structure(coding part)???

Oleksandr Kulchytskyi 19-Dec-12 3:35am

Ok.
Well, personally for me,it would be preferable to work in Wpf MVVM with conjunction of third-party Library called MvvmLight (Galasoft.MvvmLight.* namespaces), by its convenience and exposing many helpfull features like Mediator , Notification, Threading. You can get it via NuGet package manager.

So let begin with our domain model.
//as far as you want to perform various validations against model, our domain model inherits IDataErrorInfo interface
public class PersonModel: GalaSoft.MvvmLight.ObservableObject,IDataErrorInfo
{
private int _id;
public int Id
{
get{return _id;}
set { if(_id!=value){_id=value; base.RaisePropertyChanged(()=>Id);}}
}
... other properties was omitted for brevity
}

ViemModel part:

public sealed class PersonViewModel:GalaSoft.MvvmLight.ViewModelBase
{
private PersonModel _curPer;
public PersonModel CurrentPerson
{
get{return _curPer;}
set
{
_curPer=value; base.RaisePropertyCahnged(()=>CurrentPerson);
}
}

private ObservableCollection<PersonModel> _perList;
public ObservableCollection<PersonModel> PersonList
{
get{return _perList;}
set
{
_perList=value; base.RaisePropertyCahnged(()=>PersonList);
}
}
// other stuff(Commands and so on) was omitted for brevity.
}

And last , you xaml:

<stackpanel datacontext="{Binding CurrentPerson}" orientation="Vertical">
<textbox text="{Binding Id,Mode=TwoWay}">
....

<ListBox ItemsSource="{Binding PersonList}" DisplayMemberPath="Id"
SelectedItem="{Binding CurrentPerson,Mode=TwoWay}"/>

Anmerin 27-Dec-12 5:56am

thnkz for ur response.Hw can we add validation to the property name and age.?

The name field should only accept alphabets and age field should be of numerical .

Can we use the following logic?/or is der any other logic??

if (!Regex.IsMatch(FirstName, "^[a-zA-Z ]+$"))
{
result = "Name doesnot contain Numerical value";
}

The class in which am doing the validation is also pasting here

public class Customer : IDataErrorInfo
{
private string name;
public string FirstName
{
get
{
return name;
}
set
{
name = value;
}
}
private int age;
public int Age
{
get
{
return age;
}
set
{
age = value;
}
}
public string company;
public String Company
{
get
{
return company;
}
set
{
company = value;
}
}
private int salary;
public int Salary
{
get
{
return salary;
}
set
{
salary = value;
}
}

#region IDataErrorInfo Members

public string Error
{
get { throw new NotImplementedException(); }
}

public string this[string columnName]
{
get
{
string result = null;
if (columnName == "FirstName")
{

if (string.IsNullOrEmpty(FirstName))
result = "Please enter a Name";
//if (!Regex.IsMatch(FirstName, "^[a-zA-Z ]+$"))
//{
// result = "Name doesnot contain Numerical value";
//}
}

if (columnName == "Age")
{
if (Age <= 0 || Age >= 99)
result = "Please enter a valid age";
}
if (columnName == "Company")
{
if (string.IsNullOrEmpty(Company))
result = "Please enter a Company Name";
}
if (columnName == "Salary")
{
if (Salary <= 0 )
result = "Not valid";
}
return result;
}
}

#endregion

Anmerin 27-Dec-12 5:57am

am getting an exception while following the method which using regex.

Oleksandr Kulchytskyi 27-Dec-12 6:03am

Please provide me with exception cotent

Oleksandr Kulchytskyi 27-Dec-12 6:19am

Not exactly what i'm expectiong for..
You said : "am getting an exception while following the method which using regex."
Where Exception???

Anmerin 27-Dec-12 6:25am

Sorry..
the exception which arises is

ArgumentNullException was unhandled by the user.
Value cannot be null.
Parameter name: input

Oleksandr Kulchytskyi 27-Dec-12 6:41am

Yep, of course it must occur,
when you declare you class:
public class Customer : IDataErrorInfo you didn't provide any initialization of your class , so as a result if you check string.IsNullOrEmpty(FirstName), it it turn, it will return true!
And last one you must also inherit in INotifyPropertyChanged interface in your entities..., without such notification WPF wont update/display values properly...

Ohh yess. one more in for error notification (display func you must add appropriate style), so for textbox it must be:

<textbox grid.row="3" grid.column="1" margin="1,1,1,1" horizontalalignment="Stretch"
="" text="{Binding Path=FirstName, ValidatesOnDataErrors=true,UpdateSourceTriiger=PropertyChanged}">

Anmerin 27-Dec-12 6:53am

I think its not need to inherit INotifyProperty here..
Am getting the validation result without using it.
if the Name field is empty ,am getting the error message which i given..
but now my task is to check whether the user input for the "name" field is of alphabets only or is der any numerical field ,en error message should be shown.i need the logic for this validation.
acutally am getting that execption whn iam codding the following for checking the name field
if (!Regex.IsMatch(FirstName, "^[a-zA-Z ]+$"))
{
result = "Name doesnot contain Numerical value";
}

Oleksandr Kulchytskyi 27-Dec-12 7:07am

As concerns INPC , i think you are completelly mistake!
What would be if you develop some input , and while try to input FirstName , now do you think does WPF will track property changes ???
My answer is now...

Oleksandr Kulchytskyi 27-Dec-12 7:05am

So, make double check! What a problem?)
if(string.IsNullOrEmpty(FirstName))
return "Name cannot be empty";
if (!Regex.IsMatch(FirstName, "^[a-zA-Z ]+$"))
result = "Name doesnot contain Numerical value";