Add more ways to extract the error messages

PropertyValidator/Exceptions/PropertyException.cs

@@ -0,0 +1,13 @@
+using PropertyValidator.Models;
+using System;
+
+namespace PropertyValidator.Exceptions
+{
+    public class PropertyException : Exception
+    {
+        public PropertyException(ValidationResultArgs validationResultArgs) : base(validationResultArgs.FirstError)
+        {
+
+        }
+    }
+}

PropertyValidator/Models/MultiValidationRule.cs

@@ -39,7 +39,7 @@ private void Target_PropertyChanged(object sender, PropertyChangedEventArgs e)
         // TODO convert to List<string>
         public override sealed string ErrorMessage => $"[{string.Join(",", ErrorsAsJsonString())}]";
 
-        private IEnumerable<string> ErrorsAsJsonString()
+        private IEnumerable<string?> ErrorsAsJsonString()
             => validationRules
                 .Where(e => e.HasError)
                 .Select(e => $"{e.PropertyName}:\"{e.ErrorMessage}\"");

PropertyValidator/PropertyValidator.csproj

@@ -11,9 +11,9 @@
     <PackageProjectUrl>https://github.com/mr5z/PropertyValidator</PackageProjectUrl>
     <RepositoryUrl>https://github.com/mr5z/PropertyValidator</RepositoryUrl>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
-    <FileVersion>1.0.6.1</FileVersion>
-    <AssemblyVersion>1.0.6.1</AssemblyVersion>
-    <Version>1.0.6.1</Version>
+    <FileVersion>1.0.6.2</FileVersion>
+    <AssemblyVersion>1.0.6.2</AssemblyVersion>
+    <Version>1.0.6.2</Version>
     <NeutralLanguage>en</NeutralLanguage>
   </PropertyGroup>
 

PropertyValidator/Services/IValidationService.cs

@@ -7,23 +7,55 @@ namespace PropertyValidator.Services
 {
     public interface IValidationService
     {
-        // For registration
+        /// <summary>
+        /// Registers the model for validation
+        /// </summary>
+        /// <typeparam name="TNotifiableModel"></typeparam>
+        /// <param name="notifiableModel">The notifiable model</param>
+        /// <param name="autofill">If true, it will automatically fills the error properties</param>
+        /// <param name="delay">Delays the fill up of error properties</param>
+        /// <returns>RuleCollection so that it can be chained</returns>
         RuleCollection<TNotifiableModel> For<TNotifiableModel>(
             TNotifiableModel notifiableModel,
             bool autofill = false,
             TimeSpan? delay = null)
             where TNotifiableModel : INotifyPropertyChanged;
 
-        // Retrieve error messages per property
+        /// <summary>
+        /// Retrieve error messages per property
+        /// </summary>
+        /// <typeparam name="TNotifiableModel"></typeparam>
+        /// <param name="_">Unused</param>
+        /// <param name="expression">Expression to extract the property name from the target class</param>
+        /// <returns>The first error message</returns>
         string? GetErrorMessage<TNotifiableModel>(
-            TNotifiableModel notifiableModel,
-            Expression<Func<TNotifiableModel, object>> expression)
+            TNotifiableModel _,
+            Expression<Func<TNotifiableModel, object?>> expression)
             where TNotifiableModel : INotifyPropertyChanged;
 
-        // Manually trigger the validation
+        /// <summary>
+        /// Retrieve error messages per property
+        /// </summary>
+        /// <typeparam name="TNotifiableModel"></typeparam>
+        /// <param name="propertyName">The name of the property the exist within the registered notifiable model</param>
+        /// <returns>The first error message</returns>
+        string? GetErrorMessage<TNotifiableModel>(string propertyName);
+
+        /// <summary>
+        /// Ensure all properties are in a valid state based from the provided validation rules
+        /// </summary>
+        /// <throws>PropertyException if there is an error</throws>
+        void EnsurePropertiesAreValid();
+
+        /// <summary>
+        /// Trigger manually the validation
+        /// </summary>
+        /// <returns></returns>
         bool Validate();
 
-        // Subscribe to error events (cleared/raised)
+        /// <summary>
+        /// Subscribe to error events (cleared/raised)
+        /// </summary>
         event EventHandler<ValidationResultArgs>? PropertyInvalid;
     }
 }

PropertyValidator/Services/ValidationService.cs

@@ -9,6 +9,7 @@
 using System.Threading.Tasks;
 using System.Threading;
 using System.Diagnostics.CodeAnalysis;
+using PropertyValidator.Exceptions;
 
 namespace PropertyValidator.Services
 {
@@ -97,13 +98,7 @@ private async Task PropertyChangedAsync(object sender, PropertyChangedEventArgs
 
             Validate(e.PropertyName);
 
-            var errorMessages = GetRules()
-                .Where(it => it.HasError && it.PropertyName == e.PropertyName)
-                .Select(it => new { it.PropertyName, ErrorMessage = it.Error })
-                .GroupBy(it => it.PropertyName)
-                .ToDictionary(group => group.Key, g => g.Select(it => it.ErrorMessage));
-
-            var eventArgs = new ValidationResultArgs(e.PropertyName, errorMessages);
+            var eventArgs = GetValidationResultArgs(e.PropertyName);
             if (autofill)
             {
                 EnsureEntryMethodInvoked();
@@ -112,12 +107,8 @@ private async Task PropertyChangedAsync(object sender, PropertyChangedEventArgs
             PropertyInvalid?.Invoke(this, eventArgs);
         }
 
-        public List<string?> GetErrorMessages<TNotifiableModel>(
-            TNotifiableModel _, 
-            Expression<Func<TNotifiableModel, object>> expression) 
-            where TNotifiableModel : INotifyPropertyChanged
+        private List<string?> GetErrorMessages(string propertyName) 
         {
-            var propertyName = expression.GetMemberName();
             return GetRules()
                 .Where(it => it.HasError && it.PropertyName == propertyName)
                 .Select(it => it.Error)
@@ -126,10 +117,16 @@ private async Task PropertyChangedAsync(object sender, PropertyChangedEventArgs
 
         public string? GetErrorMessage<TNotifiableModel>(
             TNotifiableModel notifiableProperty, 
-            Expression<Func<TNotifiableModel, object>> expression) 
+            Expression<Func<TNotifiableModel, object?>> expression) 
             where TNotifiableModel : INotifyPropertyChanged
         {
-            return GetErrorMessages(notifiableProperty, expression).FirstOrDefault();
+            var propertyName = expression.GetMemberName();
+            return GetErrorMessages(propertyName).FirstOrDefault();
+        }
+
+        public string? GetErrorMessage<TNotifiableModel>(string propertyName)
+        {
+            return GetErrorMessages(propertyName).FirstOrDefault();
         }
 
         public bool HasError()
@@ -147,6 +144,16 @@ public bool Validate([NotNull] string propertyName)
             return ValidateImpl(propertyName);
         }
 
+        private ValidationResultArgs GetValidationResultArgs(string propertyName)
+        {
+            var errorMessages = GetRules()
+                .Where(it => it.HasError && it.PropertyName == propertyName)
+                .Select(it => new { it.PropertyName, ErrorMessage = it.Error })
+                .GroupBy(it => it.PropertyName)
+                .ToDictionary(group => group.Key, g => g.Select(it => it.ErrorMessage));
+            return new ValidationResultArgs(propertyName, errorMessages);
+        }
+
         private bool ValidateImpl(string? propertyName = null)
         {
             EnsureEntryMethodInvoked();
@@ -177,5 +184,13 @@ public static bool ValidateRuleCollection(
             }
             return noErrors;
         }
+
+        public void EnsurePropertiesAreValid()
+        {
+            var resultArgs = GetValidationResultArgs(string.Empty);
+            var firstError = resultArgs.FirstError;
+            if (!string.IsNullOrEmpty(firstError))
+                throw new PropertyException(resultArgs);
+        }
     }
 }