Validation on WPF Options - wpf

Question

I have been sitting on the internet now for 3hours with not much help.
I am trying to implement validation on my UI with the following requirements using the MVVM principle.
Currently by using DataAnnotations on my model:
Example:
private string _name;
[Required(ErrorMessage = "Name must be filled")]
public string Name
{
get { return _name; }
set { this.Update(x => x.Name, () => _name= value, _name, value); }
}
1) I want the validation only to be done when I click on a button (Submit)
2) If I have lets say 5 validations on the UI I want to display them in a list also.
I had a look at several ways and not sure which to use for best practices that suits my 2 requirements the best:
IDataInfoError?
INotifyDataErrorInfo?
DataAnnotations? (Current implementation)
Anybody that can point me in the right direction, tips anything?

Answer 1

You should read the following blog post: https://blog.magnusmontin.net/2013/08/26/data-validation-in-wpf/. It provides an example of you could implement validation using data annotations and the INotifyDataErrorInfo interface:
public class ViewModel : INotifyDataErrorInfo
{
private readonly Dictionary<string, ICollection<string>>
_validationErrors = new Dictionary<string, ICollection<string>>();
private readonly Model _user = new Model();
public string Username
{
get { return _user.Username; }
set
{
_user.Username = value;
ValidateModelProperty(value, "Username");
}
}
public string Name
{
get { return _user.Name; }
set
{
_user.Name = value;
ValidateModelProperty(value, "Name");
}
}
protected void ValidateModelProperty(object value, string propertyName)
{
if (_validationErrors.ContainsKey(propertyName))
_validationErrors.Remove(propertyName);
ICollection<ValidationResult> validationResults = new List<ValidationResult>();
ValidationContext validationContext =
new ValidationContext(_user, null, null) { MemberName = propertyName };
if (!Validator.TryValidateProperty(value, validationContext, validationResults))
{
_validationErrors.Add(propertyName, new List<string>());
foreach (ValidationResult validationResult in validationResults)
{
_validationErrors[propertyName].Add(validationResult.ErrorMessage);
}
}
RaiseErrorsChanged(propertyName);
}
protected void ValidateModel()
{
_validationErrors.Clear();
ICollection<ValidationResult> validationResults = new List<ValidationResult>();
ValidationContext validationContext = new ValidationContext(_user, null, null);
if (!Validator.TryValidateObject(_user, validationContext, validationResults, true))
{
foreach (ValidationResult validationResult in validationResults)
{
string property = validationResult.MemberNames.ElementAt(0);
if (_validationErrors.ContainsKey(property))
{
_validationErrors[property].Add(validationResult.ErrorMessage);
}
else
{
_validationErrors.Add(property, new List<string> { validationResult.ErrorMessage });
}
}
}
/* Raise the ErrorsChanged for all properties explicitly */
RaiseErrorsChanged("Username");
RaiseErrorsChanged("Name");
}
public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
private void RaiseErrorsChanged(string propertyName)
{
if (ErrorsChanged != null)
ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
}
public System.Collections.IEnumerable GetErrors(string propertyName)
{
if (string.IsNullOrEmpty(propertyName)
|| !_validationErrors.ContainsKey(propertyName))
return null;
return _validationErrors[propertyName];
}
public bool HasErrors
{
get { return _validationErrors.Count > 0; }
}
}