diff --git a/PacticeSolution/LinqInNotIn/LinqInNotIn.csproj b/PacticeSolution/LinqInNotIn/LinqInNotIn.csproj
new file mode 100644
index 0000000..74abf5c
--- /dev/null
+++ b/PacticeSolution/LinqInNotIn/LinqInNotIn.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
diff --git a/PacticeSolution/LinqInNotIn/Product.cs b/PacticeSolution/LinqInNotIn/Product.cs
new file mode 100644
index 0000000..bf74f27
--- /dev/null
+++ b/PacticeSolution/LinqInNotIn/Product.cs
@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace LinqInNotIn
+{
+    internal class Product
+    {
+        public int ProductId { get; set; }
+        public string Name { get; set; }
+
+        public Product(int id, string name)
+        {
+            this.ProductId = id;
+            this.Name = name;
+        }
+    }
+}
diff --git a/PacticeSolution/LinqInNotIn/Program.cs b/PacticeSolution/LinqInNotIn/Program.cs
new file mode 100644
index 0000000..64f5da4
--- /dev/null
+++ b/PacticeSolution/LinqInNotIn/Program.cs
@@ -0,0 +1,42 @@
+namespace LinqInNotIn
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            List<Product> products = new List<Product>();
+            products.Add(new Product(1, "Scissors"));
+            products.Add(new Product(2, "Pencil"));
+            products.Add(new Product(3, "Ballpen"));
+            //products.Add(new Product(3, "Null Ballpen"));
+            products.Add(new Product(4, "Snack"));
+            products.Add(new Product(5, "Beverage"));
+
+            int[] ids = { 2, 4, 5 };
+            
+            var inQuery = from item in products
+                        where ids.Contains(item.ProductId)
+                        select item;
+
+            var notInQuery = from item in products
+                             where !ids.Contains(item.ProductId)
+                             select item;
+
+            Console.WriteLine("inQuery");
+            foreach (var item in inQuery)
+            {
+                Console.WriteLine($"idx: {item.ProductId}, name: {item.Name}");
+            }
+
+            Console.WriteLine("notInQuery");
+            foreach (var item in notInQuery)
+            {
+                Console.WriteLine($"idx: {item.ProductId}, name: {item.Name}");
+            }
+
+            var firstItem = products.First(item => item.ProductId == 3);
+            var singleItem = products.Single(item => item.ProductId == 3);
+            Console.WriteLine($"first == single: {firstItem == singleItem}");
+        }
+    }
+}
\ No newline at end of file
diff --git a/PacticeSolution/PacticeSolution.sln b/PacticeSolution/PacticeSolution.sln
index 93d6085..2143681 100644
--- a/PacticeSolution/PacticeSolution.sln
+++ b/PacticeSolution/PacticeSolution.sln
@@ -121,6 +121,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DataTemplateSample", "DataT
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CommandSample", "CommandSample\CommandSample.csproj", "{AFB4006F-917A-4358-898F-8C4DC0A1E6C8}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "LinqInNotIn", "LinqInNotIn\LinqInNotIn.csproj", "{9261D8E1-5DEE-4329-AB32-946AD5E69C66}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -363,6 +365,10 @@ Global
 		{AFB4006F-917A-4358-898F-8C4DC0A1E6C8}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{AFB4006F-917A-4358-898F-8C4DC0A1E6C8}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{AFB4006F-917A-4358-898F-8C4DC0A1E6C8}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9261D8E1-5DEE-4329-AB32-946AD5E69C66}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9261D8E1-5DEE-4329-AB32-946AD5E69C66}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9261D8E1-5DEE-4329-AB32-946AD5E69C66}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9261D8E1-5DEE-4329-AB32-946AD5E69C66}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE