Issue 27

README.md

@@ -22,6 +22,7 @@ Currently the following is supported:
 - Not Null constraint
 - Auto increment (An int PrimaryKey will automatically be incremented)
 - Index (Decorate columns with the `Index` attribute. Indices are automatically created for foreign keys by default. To prevent this you can remove the convetion `ForeignKeyIndexConvention`)
+- Unique constraint (Decorate columsn with the `UniqueAttribute` which is part of this library)
 
 I tried to write the code in a extensible way.
 The logic is divided into two main parts, Builder and Statement.

SQLite.CodeFirst.Console/Entity/Player.cs

@@ -6,6 +6,7 @@ namespace SQLite.CodeFirst.Console.Entity
     public class Player : Person
     {
         [Index] // Automatically named 'IX_TeamPlayer_Number'
+        [Unique(OnConflictAction.Fail)]
         public int Number { get; set; }
 
         public virtual Team Team { get; set; }

SQLite.CodeFirst.Test/SQLite.CodeFirst.Test.csproj

@@ -80,6 +80,7 @@
     <Compile Include="Statement\ColumnConstraint\MaxLengthConstraint.cs" />
     <Compile Include="Statement\ColumnConstraint\ColumnConstraintCollectionTest.cs" />
     <Compile Include="Statement\ColumnConstraint\NotNullConstraintTest.cs" />
+    <Compile Include="Statement\ColumnConstraint\UniqueConstraintTest.cs" />
     <Compile Include="Statement\ColumnStatementCollectionTest.cs" />
     <Compile Include="Statement\PrimaryKeyStatementTest.cs" />
     <Compile Include="Statement\CreateDatabaseStatementTest.cs" />

SQLite.CodeFirst.Test/Statement/ColumnConstraint/UniqueConstraintTest.cs

@@ -0,0 +1,27 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using SQLite.CodeFirst.Statement.ColumnConstraint;
+
+namespace SQLite.CodeFirst.Test.Statement.ColumnConstraint
+{
+    [TestClass]
+    public class UniqueConstraintTest
+    {
+        [TestMethod]
+        public void CreateStatement_StatementIsCorrect_NoConstraint()
+        {
+            var uniqueConstraint = new UniqueConstraint();
+            uniqueConstraint.OnConflict = OnConflictAction.None;
+            string output = uniqueConstraint.CreateStatement();
+            Assert.AreEqual(output, "UNIQUE");
+        }
+
+        [TestMethod]
+        public void CreateStatement_StatementIsCorrect_WithConstraint()
+        {
+            var uniqueConstraint = new UniqueConstraint();
+            uniqueConstraint.OnConflict = OnConflictAction.Rollback;
+            string output = uniqueConstraint.CreateStatement();
+            Assert.AreEqual(output, "UNIQUE ON CONFLICT ROLLBACK");
+        }
+    }
+}

SQLite.CodeFirst/Attributes/OnConflictAction.cs

@@ -0,0 +1,16 @@
+namespace SQLite.CodeFirst
+{
+    /// <summary>
+    /// The action to resolve a UNIQUE constraint violation.
+    /// Is used together with the <see cref="UniqueAttribute"/>.
+    /// </summary>
+    public enum OnConflictAction
+    {
+        None,
+        Rollback,
+        Abort,
+        Fail,
+        Ignore,
+        Replace
+    }
+}

SQLite.CodeFirst/Attributes/UniqueAttribute.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace SQLite.CodeFirst
+{
+    /// <summary>
+    /// The UNIQUE Constraint prevents two records from having identical values in a particular column.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property)]
+    public sealed class UniqueAttribute : Attribute
+    {
+        public UniqueAttribute(OnConflictAction onConflict = OnConflictAction.None)
+        {
+            OnConflict = onConflict;
+        }
+
+        public OnConflictAction OnConflict { get; set; }
+    }
+}

SQLite.CodeFirst/DbInitializers/SqliteInitializerBase.cs

@@ -3,6 +3,7 @@
 using System.Data.Entity.ModelConfiguration.Conventions;
 using SQLite.CodeFirst.Convention;
 using System.IO;
+using System.Linq;
 using SQLite.CodeFirst.Utility;
 
 namespace SQLite.CodeFirst
@@ -36,6 +37,10 @@ protected SqliteInitializerBase(DbModelBuilder modelBuilder)
             // See https://github.com/msallin/SQLiteCodeFirst/issues/7 for details.
             modelBuilder.Conventions.Remove<TimestampAttributeConvention>();
 
+            modelBuilder.Properties()
+                .Having(x => x.GetCustomAttributes(false).OfType<UniqueAttribute>().FirstOrDefault())
+                .Configure((config, attribute) => config.HasColumnAnnotation("IsUnique", attribute));
+
             // By default there is a 'ForeignKeyIndexConvention' but it can be removed.
             // And there is no "Contains" and no way to enumerate the ConventionsCollection.
             // So a try/catch will do the job.

SQLite.CodeFirst/Internal/Builder/ColumnStatementCollectionBuilder.cs

@@ -36,6 +36,7 @@ private IEnumerable<ColumnStatement> CreateColumnStatements()
                 AddMaxLengthConstraintIfNecessary(property, columnStatement);
                 AdjustDatatypeForAutogenerationIfNecessary(property, columnStatement);
                 AddNullConstraintIfNecessary(property, columnStatement);
+                AddUniqueConstraintIfNecessary(property, columnStatement);
 
                 yield return columnStatement;
             }
@@ -66,5 +67,19 @@ private static void AddNullConstraintIfNecessary(EdmProperty property, ColumnSta
                 columnStatement.ColumnConstraints.Add(new NotNullConstraint());
             }
         }
+
+        private static void AddUniqueConstraintIfNecessary(EdmProperty property, ColumnStatement columnStatement)
+        {
+            MetadataProperty item;
+            bool found = property.MetadataProperties.TryGetValue("http://schemas.microsoft.com/ado/2013/11/edm/customannotation:IsUnique", true, out item);
+            if (found)
+            {
+                var value = (UniqueAttribute)item.Value;
+                columnStatement.ColumnConstraints.Add(new UniqueConstraint
+                {
+                    OnConflict = value.OnConflict
+                });
+            }
+        }
     }
 }

SQLite.CodeFirst/Internal/Statement/ColumnConstraint/UniqueConstraint.cs

@@ -0,0 +1,20 @@
+using System.Text;
+
+namespace SQLite.CodeFirst.Statement.ColumnConstraint
+{
+    internal class UniqueConstraint : IColumnConstraint
+    {
+        private const string Template = "UNIQUE {conflict-clause}";
+
+        public OnConflictAction OnConflict { get; set; }
+
+        public string CreateStatement()
+        {
+            var sb = new StringBuilder(Template);
+
+            sb.Replace("{conflict-clause}", OnConflict != OnConflictAction.None ? "ON CONFLICT " + OnConflict.ToString().ToUpperInvariant() : string.Empty);
+
+            return sb.ToString().Trim();
+        }
+    }
+}

SQLite.CodeFirst/SQLite.CodeFirst.csproj

@@ -83,10 +83,13 @@
     <Compile Include="..\Shared\AssemblySharedInfo.cs">
       <Link>Properties\AssemblySharedInfo.cs</Link>
     </Compile>
+    <Compile Include="Attributes\OnConflictAction.cs" />
+    <Compile Include="Attributes\UniqueAttribute.cs" />
     <Compile Include="Entities\IHistory.cs" />
     <Compile Include="Internal\Builder\NameCreators\IndexNameCreator.cs" />
     <Compile Include="Internal\Builder\NameCreators\SpecialChars.cs" />
     <Compile Include="IDatabaseCreator.cs" />
+    <Compile Include="Internal\Statement\ColumnConstraint\UniqueConstraint.cs" />
     <Compile Include="Internal\Utility\HashCreator.cs" />
     <Compile Include="Internal\Utility\HistoryEntityTypeValidator.cs" />
     <Compile Include="ISqliteSqlGenerator.cs" />