.NET Community Toolkit is a collection of helpers and APIs that work for all .NET developers and are agnostic of any specific UI platform. The toolkit is maintained and published by Microsoft, and part of the .NET Foundation.
We already have the [NotifyDataErrorInfo] attribute, which adds source generation to validate this property.
But since we can use custom validation methods to perform multi-property validation, we should have a way to indicate that Property A influences the validation of Property B.
API breakdown
Add an attribute, NotifyDataErrorInfoForAttribute, which influences the source generator to add validation of other properties.
Right now, the generated setter for a property with [NotifyDataErrorInfo] looks like this:
if (!global::System.Collections.Generic.EqualityComparer<string?>.Default.Equals(path, value))
{
OnPathChanging(value);
OnPathChanging(default, value);
OnPropertyChanging(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangingArgs.Path);
path = value;
ValidateProperty(value, "Path");
ValidateProperty(SomeOtherProperty,"SomeOtherProperty"); // <---- THIS LINE IS NEW
OnPathChanged(value);
OnPathChanged(default, value);
OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.Path);
}
Usage example
[NotifyDataErrorInfoFor(nameof(Path))] // <--- NEW ATTRIBUTE
private bool isRequired;
[ObservableProperty]
[NotifyDataErrorInfo]
[CustomValidation(typeof(FileSystemLocationViewModel), nameof(ValidatePath))]
private string? path;
public static ValidationResult? ValidatePath(string? path, ValidationContext context)
{
var instance = (FileSystemLocationViewModel)context.ObjectInstance;
if (string.IsNullOrWhiteSpace(path))
{
if (instance.IsRequired)
return new ValidationResult("Path is required");
return ValidationResult.Success;
}
if(IsValidPath(path))
return ValidationResult.Success;
return new ValidationResult("Invalid path provided");
}
Breaking change?
No
Alternatives
Workaround (available now):
Manually implement the property
private bool isRequired;
public bool IsRequired
{
get => this.isRequired;
set
{
if (this.SetProperty(ref this.isRequired, value))
this.ValidateProperty(this.Path, nameof(this.Path));
}
}
Overview
We already have the
[NotifyDataErrorInfo]attribute, which adds source generation to validate this property.But since we can use custom validation methods to perform multi-property validation, we should have a way to indicate that Property A influences the validation of Property B.
API breakdown
Add an attribute,
NotifyDataErrorInfoForAttribute, which influences the source generator to add validation of other properties.Right now, the generated setter for a property with
[NotifyDataErrorInfo]looks like this:After the change, it would look like this:
Usage example
Breaking change?
No
Alternatives
Workaround (available now):
Manually implement the property
Additional context
No response
Help us help you
No, just wanted to propose this