Validations

Author: chanan

README.md

@@ -163,6 +163,10 @@ As you can see in the example above BlazorDB will detect associations added to t
 
 **Note:** At this time removing/deleting is not done automatically and needs to be done manually. A future update of BlazorDB will handle deletions properly.  
 
+## Validations
+
+You can annotate your model's propeties with `[Required]` and `[MaxLength(int)]` to enforce required and max length on properties.
+
 ## Example
 
 A Todo sample built with BlazorDB is included in the sample project:

src/BlazorDB/BlazorDB.csproj

@@ -7,7 +7,7 @@
     <BlazorLinkOnBuild>false</BlazorLinkOnBuild>
     <LangVersion>7.3</LangVersion>
     <PackageId>BlazorDB</PackageId>
-    <Version>0.1.2</Version>
+    <Version>0.1.3</Version>
     <Authors>Chanan Braunstein</Authors>
     <Title>Blazor localStorage Database</Title>
     <Description>In memory, persisted to localstorage, database for .net Blazor browser framework</Description>

src/BlazorDB/BlazorDBUpdateException.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace BlazorDB
+{
+    public class BlazorDBUpdateException : Exception
+    {
+        public BlazorDBUpdateException(string error) : base(error)
+        {
+        } 
+    }
+}

src/BlazorDB/DataAnnotations/MaxLength.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace BlazorDB.DataAnnotations
+{
+    [AttributeUsage(AttributeTargets.Property)]
+    public class MaxLength : Attribute
+    {
+        public MaxLength(int length)
+        {
+            this.length = length;
+        }
+
+        internal int length;
+    }
+}

src/BlazorDB/DataAnnotations/Required.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace BlazorDB.DataAnnotations
+{
+    [AttributeUsage(AttributeTargets.Property)]
+    public class Required : Attribute
+    {
+    }
+}

src/BlazorDB/Storage/StorageManagerSave.cs

@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using BlazorDB.DataAnnotations;
 using Microsoft.AspNetCore.Blazor;
 
 namespace BlazorDB.Storage
@@ -15,12 +16,73 @@ public int SaveContextToLocalStorage(StorageContext context)
             var contextType = context.GetType();
             Logger.ContextSaved(contextType);
             var storageSets = StorageManagerUtil.GetStorageSets(contextType);
-            var metadataMap = LoadMetadataList(context, storageSets, contextType);
-            total = SaveStorageSets(context, total, contextType, storageSets, metadataMap);
-            Logger.EndGroup();
+            var error = ValidateModels(context, storageSets);
+            if (error == null)
+            {
+                var metadataMap = LoadMetadataList(context, storageSets, contextType);
+                total = SaveStorageSets(context, total, contextType, storageSets, metadataMap);
+                Logger.EndGroup();
+            }
+            else
+            {
+                BlazorLogger.Logger.Error("SaveChanges() terminated due to validation error");
+                Logger.EndGroup();
+                throw new BlazorDBUpdateException(error);
+            }
+            
             return total;
         }
 
+        private string ValidateModels(StorageContext context, IEnumerable<PropertyInfo> storageSets)
+        {
+            string error = null;
+            foreach (var storeageSetProp in storageSets)
+            {
+                var storeageSet = storeageSetProp.GetValue(context);
+                var listProp = storeageSet.GetType().GetProperty(StorageManagerUtil.List, StorageManagerUtil.Flags);
+                var list = listProp.GetValue(storeageSet);
+                var method = list.GetType().GetMethod(StorageManagerUtil.GetEnumerator);
+                var enumerator = (IEnumerator)method.Invoke(list, new object[] { });
+                while (enumerator.MoveNext())
+                {
+                    var model = enumerator.Current;
+                    foreach (var prop in model.GetType().GetProperties())
+                    {
+                        if (Attribute.IsDefined(prop, typeof(Required)))
+                        {
+                            var value = prop.GetValue(model);
+                            if (value == null)
+                            {
+                                error =
+                                    $"{model.GetType().FullName}.{prop.Name} is a required field. SaveChanges() has been terminated.";
+                                break;
+                            }
+                        }
+
+                        if (Attribute.IsDefined(prop, typeof(MaxLength)))
+                        {
+                            var maxLength = (MaxLength) Attribute.GetCustomAttribute(prop, typeof(MaxLength));
+                            var value = prop.GetValue(model);
+                            if (value != null)
+                            {
+                                var str = value.ToString();
+                                if (str.Length > maxLength.length)
+                                {
+                                    error =
+                                        $"{model.GetType().FullName}.{prop.Name} length is longer than {maxLength.length}. SaveChanges() has been terminated.";
+                                    break;
+                                }
+                            }
+                        }
+                    }
+
+                    if (error != null) break;
+                }
+            }
+
+            return error;
+        }
+
         private static IReadOnlyDictionary<string, Metadata> LoadMetadataList(StorageContext context,
             IEnumerable<PropertyInfo> storageSets, Type contextType)
         {

src/Sample/Models/Person.cs

@@ -1,11 +1,14 @@
 using System.Collections.Generic;
+using BlazorDB.DataAnnotations;
 
 namespace Sample.Models
 {
     public class Person
     {
         public int Id { get; set; }
+        [Required]
         public string FirstName { get; set; }
+        [MaxLength(20)]
         public string LastName { get; set; }
         public Address HomeAddress { get; set; }
         public List<Address> OtherAddresses { get; set; }

src/Sample/Pages/Index.cshtml

@@ -12,6 +12,11 @@
 
 <button onclick="@OnclickSaveChanges">SaveChanges</button>
 
+<h2>Validations</h2>
+
+<button onclick="@OnRequired">Required</button>
+
+<button onclick="@OnMaxLength">Max Length</button>
 
 @if (@Person != null)
 {
@@ -54,4 +59,18 @@
     {
         Context.SaveChanges();
     }
+
+    void OnRequired()
+    {
+        var person = new Person {LastName = "Firstname required!"};
+        Context.People.Add(person);
+        Context.SaveChanges();
+    }
+
+    void OnMaxLength()
+    {
+        var person = new Person { FirstName = "Lastname is long", LastName = "This is a very long last name and should throw!" };
+        Context.People.Add(person);
+        Context.SaveChanges();
+    }
 }