MiniValidation
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A minimalist validation library for .NET built atop the existing features in `System.ComponentModel.DataAnnotations` namespace
MiniValidation
A minimalistic validation library built atop the existing features in .NET's System.ComponentModel.DataAnnotations
namespace. Adds support for single-line validation calls and recursion with cycle detection.
Supports .NET Standard 2.0 compliant runtimes.
Installation
Install the library from NuGet:
❯ dotnet add package MiniValidation
ASP.NET Core 6+ Projects
If installing into an ASP.NET Core 6+ project, consider using the MinimalApis.Extensions package instead, which adds extensions specific to ASP.NET Core, including a validation endpoint filter for .NET 7 apps:
❯ dotnet add package MinimalApis.Extensions
Example usage
Validate an object
var widget = new Widget { Name = "" };
var isValid = MiniValidator.TryValidate(widget, out var errors);
class Widget
{
[Required, MinLength(3)]
public string Name { get; set; }
public override string ToString() => Name;
}
Use services from validators
var widget = new Widget { Name = "" };
// Get your serviceProvider from wherever makes sense
var serviceProvider = ...
var isValid = MiniValidator.TryValidate(widget, serviceProvider, out var errors);
class Widget : IValidatableObject
{
[Required, MinLength(3)]
public string Name { get; set; }
public override string ToString() => Name;
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
var disallowedNamesService = validationContext.GetService(typeof(IDisallowedNamesService)) as IDisallowedNamesService;
if (disallowedNamesService is null)
{
throw new InvalidOperationException($"Validation of {nameof(Widget)} requires an {nameof(IDisallowedNamesService)} instance.");
}
if (disallowedNamesService.IsDisallowedName(Name))
{
yield return new($"Cannot name a widget '{Name}'.", new[] { nameof(Name) });
}
}
}
Console app
using System.ComponentModel.DataAnnotations;
using MiniValidation;
var title = args.Length > 0 ? args[0] : "";
var widgets = new List<Widget>
{
new Widget { Name = title },
new WidgetWithCustomValidation { Name = title }
};
foreach (var widget in widgets)
{
if (!MiniValidator.TryValidate(widget, out var errors))
{
Console.WriteLine($"{nameof(Widget)} has errors!");
foreach (var entry in errors)
{
Console.WriteLine($" {entry.Key}:");
foreach (var error in entry.Value)
{
Console.WriteLine($" - {error}");
}
}
}
else
{
Console.WriteLine($"{nameof(Widget)} '{widget}' is valid!");
}
}
class Widget
{
[Required, MinLength(3)]
public string Name { get; set; }
public override string ToString() => Name;
}
class WidgetWithCustomValidation : Widget, IValidatableObject
{
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (string.Equals(Name, "Widget", StringComparison.OrdinalIgnoreCase))
{
yield return new($"Cannot name a widget '{Name}'.", new[] { nameof(Name) });
}
}
}
❯ widget.exe
Widget 'widget' is valid!
Widget has errors!
Name:
- Cannot name a widget 'widget'.
❯ widget.exe Ok
Widget has errors!
Name:
- The field Name must be a string or array type with a minimum length of '3'.
Widget has errors!
Name:
- The field Name must be a string or array type with a minimum length of '3'.
❯ widget.exe Widget
Widget 'Widget' is valid!
Widget has errors!
Name:
- Cannot name a widget 'Widget'.
❯ widget.exe MiniValidation
Widget 'MiniValidation' is valid!
Widget 'MiniValidation' is valid!
Web app (.NET 6)
using System.ComponentModel.DataAnnotations;
using MiniValidation;
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/", () => "Hello World");
app.MapGet("/widgets", () =>
new[] {
new Widget { Name = "Shinerizer" },
new Widget { Name = "Sparklizer" }
});
app.MapGet("/widgets/{name}", (string name) =>
new Widget { Name = name });
app.MapPost("/widgets", (Widget widget) =>
!MiniValidator.TryValidate(widget, out var errors)
? Results.ValidationProblem(errors)
: Results.Created($"/widgets/{widget.Name}", widget));
app.MapPost("/widgets/custom-validation", (WidgetWithCustomValidation widget) =>
!MiniValidator.TryValidate(widget, out var errors)
? Results.ValidationProblem(errors)
: Results.Created($"/widgets/{widget.Name}", widget));
app.Run();
class Widget
{
[Required, MinLength(3)]
public string? Name { get; set; }
public override string? ToString() => Name;
}
class WidgetWithCustomValidation : Widget, IValidatableObject
{
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (string.Equals(Name, "Widget", StringComparison.OrdinalIgnoreCase))
{
yield return new($"Cannot name a widget '{Name}'.", new[] { nameof(Name) });
}
}
}