Add typed join specification builder syntax

DynamORM/Builders/IDynamicTypedSelectQueryBuilder.cs

@@ -43,6 +43,12 @@ namespace DynamORM.Builders
         /// <returns>Builder instance.</returns>
         IDynamicTypedSelectQueryBuilder<T> Join<TRight>(Expression<Func<T, TRight, bool>> on, string alias = null, DynamicJoinType joinType = DynamicJoinType.Inner);
 
+        /// <summary>Add typed join using join-spec builder syntax (<c>As()</c>, join kind and <c>On()</c>).</summary>
+        /// <typeparam name="TRight">Joined mapped entity type.</typeparam>
+        /// <param name="specification">Join specification builder callback.</param>
+        /// <returns>Builder instance.</returns>
+        IDynamicTypedSelectQueryBuilder<T> Join<TRight>(Func<TypedJoinBuilder<T, TRight>, TypedJoinBuilder<T, TRight>> specification);
+
         /// <summary>Add INNER JOIN using typed ON predicate.</summary>
         IDynamicTypedSelectQueryBuilder<T> InnerJoin<TRight>(Expression<Func<T, TRight, bool>> on, string alias = null);
 

DynamORM/Builders/Implementation/DynamicTypedSelectQueryBuilder.cs

@@ -104,6 +104,20 @@ namespace DynamORM.Builders.Implementation
             return this;
         }
 
+        public IDynamicTypedSelectQueryBuilder<T> Join<TRight>(Func<TypedJoinBuilder<T, TRight>, TypedJoinBuilder<T, TRight>> specification)
+        {
+            if (specification == null)
+                throw new ArgumentNullException("specification");
+
+            TypedJoinBuilder<T, TRight> spec = specification(new TypedJoinBuilder<T, TRight>());
+            if (spec == null)
+                throw new ArgumentException("Join specification cannot resolve to null.", "specification");
+            if (spec.OnPredicate == null)
+                throw new ArgumentException("Join specification must define ON predicate.", "specification");
+
+            return Join(spec.OnPredicate, spec.Alias, spec.JoinType);
+        }
+
         public IDynamicTypedSelectQueryBuilder<T> InnerJoin<TRight>(Expression<Func<T, TRight, bool>> on, string alias = null)
         {
             return Join(on, alias, DynamicJoinType.Inner);

DynamORM/Builders/TypedJoinBuilder.cs

@@ -0,0 +1,76 @@
+/*
+ * DynamORM - Dynamic Object-Relational Mapping library.
+ * Copyright (c) 2012-2026, Grzegorz Russek (grzegorz.russek@gmail.com)
+ * All rights reserved.
+ */
+
+using System;
+using System.Linq.Expressions;
+
+namespace DynamORM.Builders
+{
+    /// <summary>Typed join specification builder used by typed fluent select queries.</summary>
+    /// <typeparam name="TLeft">Left side mapped type.</typeparam>
+    /// <typeparam name="TRight">Right side mapped type.</typeparam>
+    public class TypedJoinBuilder<TLeft, TRight>
+    {
+        internal TypedJoinBuilder()
+        {
+            JoinType = DynamicJoinType.Inner;
+        }
+
+        /// <summary>Gets join alias.</summary>
+        public string Alias { get; private set; }
+
+        /// <summary>Gets join type.</summary>
+        public DynamicJoinType JoinType { get; private set; }
+
+        /// <summary>Gets ON predicate.</summary>
+        public Expression<Func<TLeft, TRight, bool>> OnPredicate { get; private set; }
+
+        /// <summary>Sets join alias.</summary>
+        public TypedJoinBuilder<TLeft, TRight> As(string alias)
+        {
+            Alias = alias;
+            return this;
+        }
+
+        /// <summary>Sets INNER JOIN.</summary>
+        public TypedJoinBuilder<TLeft, TRight> Inner()
+        {
+            JoinType = DynamicJoinType.Inner;
+            return this;
+        }
+
+        /// <summary>Sets LEFT JOIN.</summary>
+        public TypedJoinBuilder<TLeft, TRight> Left()
+        {
+            JoinType = DynamicJoinType.Left;
+            return this;
+        }
+
+        /// <summary>Sets RIGHT JOIN.</summary>
+        public TypedJoinBuilder<TLeft, TRight> Right()
+        {
+            JoinType = DynamicJoinType.Right;
+            return this;
+        }
+
+        /// <summary>Sets FULL JOIN.</summary>
+        public TypedJoinBuilder<TLeft, TRight> Full()
+        {
+            JoinType = DynamicJoinType.Full;
+            return this;
+        }
+
+        /// <summary>Sets ON predicate.</summary>
+        public TypedJoinBuilder<TLeft, TRight> On(Expression<Func<TLeft, TRight, bool>> predicate)
+        {
+            if (predicate == null)
+                throw new ArgumentNullException("predicate");
+
+            OnPredicate = predicate;
+            return this;
+        }
+    }
+}