Add validation attribute for Coordination numbers (#152)

* Add validation attribute for Coordination numbers

* Update README.md

Correct error in README.

* Update validation error message to correct coordination number format

* Update test data and source link

---------

Co-authored-by: Tor Seldén <tor.selden@nethouse.se>
Co-authored-by: Peter Örneholm <peter@orneholm.com>

README.md

@@ -192,7 +192,21 @@ Therefore they are exposed as extension methods in the C# api and are suffixed w
 
 #### ASP.NET Core MVC
 
-CoordinationNumberAttribute: To be added.
+If used to validate input in an ASP.NET Core MVC project, the `CoordinationNumberAttribute` can be used like this:
+
+```c#
+public class SampleDataModel
+{
+    [CoordinationNumber]
+    public string CoordinationNumber { get; set; }
+}
+```
+
+The `CoordinationNumberAttribute` attribute is available through a separate package:
+
+```console
+dotnet add package ActiveLogin.Identity.Swedish.AspNetCore
+```
 
 ### 3. Use the library in your F# project
 

src/ActiveLogin.Identity.Swedish.AspNetCore/Validation/CoordinationNumberAttribute.cs

@@ -0,0 +1,43 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace ActiveLogin.Identity.Swedish.AspNetCore.Validation
+{
+    /// <summary>
+    /// Validates a Swedish Coordination Number using <see cref="CoordinationNumber"/>.
+    /// </summary>
+    public class CoordinationNumberAttribute : ValidationAttribute
+    {
+        /// <summary>Initializes a new instance of the <see cref="CoordinationNumberAttribute"></see> class.</summary>
+        public CoordinationNumberAttribute()
+            : base("{0} is not a valid Swedish Coordination Number. It should follow a valid pattern such as YYMMDD-IIIC, YYMMDD+IIIC or YYYYMMDDIIIC.")
+        { }
+
+        /// <summary>Initializes a new instance of the <see cref="CoordinationNumberAttribute"></see> class by using the function that enables access to validation resources.</summary>
+        /// <param name="errorMessageAccessor">The function that enables access to validation resources.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="errorMessageAccessor">errorMessageAccessor</paramref> is null.</exception>
+        public CoordinationNumberAttribute(Func<string> errorMessageAccessor) : base(errorMessageAccessor)
+        { }
+
+        /// <summary>Initializes a new instance of the <see cref="CoordinationNumberAttribute"></see> class by using the error message to associate with a validation control.</summary>
+        /// <param name="errorMessage">The error message to associate with a validation control.</param>
+        public CoordinationNumberAttribute(string errorMessage) : base(errorMessage)
+        { }
+
+        /// <summary>Validates the specified Swedish Coordination Number with respect to the current validation attribute.</summary>
+        /// <param name="value">The Swedish Coordination Number to validate.</param>
+        /// <param name="validationContext">The context information about the validation operation.</param>
+        /// <returns>An instance of the <see cref="System.ComponentModel.DataAnnotations.ValidationResult"></see> class.</returns>
+        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+        {
+            var valueString = (string) value;
+            if (!CoordinationNumber.TryParse(valueString, out _))
+            {
+                var errorMessage = FormatErrorMessage(validationContext.DisplayName);
+                return new ValidationResult(errorMessage);
+            }
+
+            return ValidationResult.Success;
+        }
+    }
+}

test/ActiveLogin.Identity.Swedish.AspNetCore.Test/Validation/SwedishCoordinationNumberAttribute_IsValid.cs

@@ -0,0 +1,49 @@
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using ActiveLogin.Identity.Swedish.AspNetCore.Validation;
+using Xunit;
+
+namespace ActiveLogin.Identity.Swedish.AspNetCore.Test.Validation
+{
+    /// <remarks>
+    /// Tested with official test Coordination Numbers from Skatteverket:
+    /// https://swedish.identityinfo.net/coordinationnumber/testdata
+    /// </remarks>
+    public class SwedishCoordinationNumberAttribute_IsValid
+    {
+        [Fact]
+        public void Returns_Valid_When_Valid_Coordination_Number()
+        {
+            var model = new SampleValidationModel("480977-2389");
+            var context = new ValidationContext(model);
+            var results = new List<ValidationResult>();
+            var isValid = Validator.TryValidateObject(model, context, results, true);
+
+            Assert.True(isValid);
+            Assert.Empty(results);
+        }
+
+        [Fact]
+        public void Returns_Invalid_When_Invalid_Coordination_Number()
+        {
+            var model = new SampleValidationModel("A");
+            var context = new ValidationContext(model);
+            var results = new List<ValidationResult>();
+            var isValid = Validator.TryValidateObject(model, context, results, true);
+
+            Assert.False(isValid);
+            Assert.Single(results);
+        }
+
+        private class SampleValidationModel
+        {
+            public SampleValidationModel(string swedishCoordinationNumber)
+            {
+                SwedishCoordinationNumber = swedishCoordinationNumber;
+            }
+
+            [CoordinationNumber]
+            public string SwedishCoordinationNumber { get; }
+        }
+    }
+}