diff --git a/.github/workflows/dotnet.yml b/.github/workflows/dotnet.yml
index a6a59da..340cd7a 100644
--- a/.github/workflows/dotnet.yml
+++ b/.github/workflows/dotnet.yml
@@ -1,9 +1,9 @@
 name: Build
 
-on: [push, pull_request]
+on: [push]
 
 jobs:
-  build:
+  build-Windows:
 
     runs-on: windows-latest
 
@@ -20,4 +20,21 @@ jobs:
     - name: Test
       run: $slnList = Get-ChildItem $foo.FullName -Recurse -Filter '*.sln'; foreach ($file in $slnList) {dotnet test $file.FullName}
 
+  build-Ubuntu:
+
+      runs-on: ubuntu-latest
+
+      steps:
+      - uses: actions/checkout@v2
+      - name: Build
+        uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: '6.x'
+      - name: Restore
+        run: for f in $(find . -name "*.sln"); do dotnet restore $f; done
+      - name: Build
+        run: for f in $(find . -name "*.sln"); do dotnet build $f; done
+      - name: Test
+        run: for f in $(find . -name "*.sln"); do dotnet test $f; done
+
 
diff --git a/List/List/List/List.sln b/List/List/List/List.sln
new file mode 100644
index 0000000..ba5b5d4
--- /dev/null
+++ b/List/List/List/List.sln
@@ -0,0 +1,31 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.1.32228.430
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "List", "List\List.csproj", "{E452EFCC-D3CF-4F34-86B6-FFF9119434ED}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ListTest", "ListTest\ListTest.csproj", "{D91A340C-44C7-462D-8304-FF4C9E6170FE}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{E452EFCC-D3CF-4F34-86B6-FFF9119434ED}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E452EFCC-D3CF-4F34-86B6-FFF9119434ED}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E452EFCC-D3CF-4F34-86B6-FFF9119434ED}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E452EFCC-D3CF-4F34-86B6-FFF9119434ED}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D91A340C-44C7-462D-8304-FF4C9E6170FE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D91A340C-44C7-462D-8304-FF4C9E6170FE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D91A340C-44C7-462D-8304-FF4C9E6170FE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D91A340C-44C7-462D-8304-FF4C9E6170FE}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {8A75F5F0-0627-4DE9-BE2B-FBB251E5CA4F}
+	EndGlobalSection
+EndGlobal
diff --git a/List/List/List/List/List.cs b/List/List/List/List/List.cs
new file mode 100644
index 0000000..9480100
--- /dev/null
+++ b/List/List/List/List/List.cs
@@ -0,0 +1,204 @@
+namespace List;
+
+using System;
+using System.Collections.Generic;
+
+/// <summary>
+/// Сlass representing a list
+/// </summary>
+/// <typeparam name="T"> type of item values in the list </typeparam>
+public class SinglyLinkedList<T> where T : IComparable<T>
+{
+    /// <summary>
+    /// Class for storing list items
+    /// </summary>
+    private class ListElement
+    {
+        public T? Value { get ; set; }
+        public ListElement? Next { get; set; }
+    }
+
+    private ListElement? head;
+    private ListElement? tail;
+
+    /// <summary>
+    /// List size
+    /// </summary>
+    public int Size { get; private set; }
+
+    /// <summary>
+    /// Function for adding an item to a list
+    /// </summary>
+    /// <param name="value">T ype of item value in the list</param>
+    public virtual void Add(T value)
+    {
+        if (value == null)
+        {
+            return;
+        }
+
+        Size++;
+        if (head == null || tail == null)
+        {
+            head = new ListElement();
+            tail = head;
+            head.Value = value;
+            return;
+        }
+
+        var newTail = new ListElement();
+        newTail.Value = value;
+        tail.Next = newTail;
+        tail = newTail;
+    }
+
+    /// <summary>
+    /// Function to remove an item from the list
+    /// </summary>
+    /// <param name="index">Item position in the list</param>
+    /// <returns>was the item in the list</returns>
+    public virtual bool RemoveAt(int index)
+    {
+        if (index >= Size || index < 0)
+        {
+            return false;
+        }
+
+        Size--;
+        if (index == 0)
+        {
+            head = head?.Next;
+            return true;
+        }
+
+        var element = head;
+        ListElement? copyElement = null;
+
+        for (int i = 0; i < index - 1; i++)
+        {
+            if (i == index - 1)
+            {
+                copyElement = element;
+            }
+
+            element = element?.Next;
+        }
+
+        if (element != null && copyElement != null)
+        {
+            copyElement.Next = element.Next;
+            element.Next = null;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Function to remove an item from the list
+    /// </summary>
+    /// <param name="value">Value to be deleted</param>
+    /// <returns>was the value in the list</returns>
+    public virtual bool Remove(T value)
+    {
+        var copyHead = head;
+        for (int i = 0; i < Size; i++)
+        {
+            while (copyHead!= null)
+            {
+                if (copyHead != null && value != null && value.Equals(copyHead.Value))
+                {
+                    RemoveAt(i);
+                    return true;
+                }
+
+                copyHead = copyHead?.Next;
+            }
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Function for changing the value of an element by index
+    /// </summary>
+    /// <param name="index">Item position in the list</param>
+    /// <param name="value">New value</param>
+    public virtual bool ChangeElement(int index, T value)
+    {
+        if (index >= Size || index < 0)
+        {
+            return false;
+        }
+
+        var element = head;
+        for (int i = 0; i < index - 1; i++)
+        {
+            element = element?.Next;
+        }
+
+        if (element != null)
+        {
+            element.Value = value;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Function for printing a list
+    /// </summary>
+    public void PrintList()
+    {
+        var element = head;
+        while (element != null)
+        {
+            Console.Write($"{element.Value} ");
+            element = element.Next;
+        }
+
+        Console.WriteLine();
+    }
+
+    /// <summary>
+    /// Function to search for an item in the list
+    /// </summary>
+    /// <param name="value">Search value</param>
+    /// <returns>Is there an item in the list</returns>
+    public bool Contains(T value)
+    {
+        var element = head;
+        while (element != null)
+        {
+            if (value != null && value.CompareTo(element.Value) == 0)
+            {
+                return true;
+            }
+
+            element = element.Next;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Function for clear list
+    /// </summary>
+    public void ClearList() => head = null;
+
+    public T GetItemByIndex(int index)
+    {
+        if (index >= Size || index < 0)
+        {
+            throw new ArgumentOutOfRangeException();
+        }
+
+        ListElement? element = head;
+        for (int i = 0; i < index; i++)
+        {
+            element = element?.Next;
+        }
+
+        return element!.Value!;
+    }
+
+}
\ No newline at end of file
diff --git a/List/List/List/List/List.csproj b/List/List/List/List/List.csproj
new file mode 100644
index 0000000..16e62dd
--- /dev/null
+++ b/List/List/List/List/List.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
diff --git a/List/List/List/List/RemoveNonExistingElementException.cs b/List/List/List/List/RemoveNonExistingElementException.cs
new file mode 100644
index 0000000..1144954
--- /dev/null
+++ b/List/List/List/List/RemoveNonExistingElementException.cs
@@ -0,0 +1,6 @@
+namespace List;
+
+/// <summary>
+/// Exception for the case of deleting a non-existent element
+/// </summary>
+public class RemoveNonExistingElementException : InvalidOperationException { }
\ No newline at end of file
diff --git a/List/List/List/List/RepeatValueException.cs b/List/List/List/List/RepeatValueException.cs
new file mode 100644
index 0000000..4ade6f3
--- /dev/null
+++ b/List/List/List/List/RepeatValueException.cs
@@ -0,0 +1,6 @@
+namespace List;
+
+/// <summary>
+/// Exception for the case of adding an existing element
+/// </summary>
+public class RepeatValueException : InvalidOperationException { }
diff --git a/List/List/List/List/UniqueList.cs b/List/List/List/List/UniqueList.cs
new file mode 100644
index 0000000..0413598
--- /dev/null
+++ b/List/List/List/List/UniqueList.cs
@@ -0,0 +1,76 @@
+namespace List;
+
+/// <summary>
+/// Class representing a list of unique values
+/// </summary>
+public class UniqueList<T> : SinglyLinkedList<T> where T : IComparable<T>
+{
+    /// <summary>
+    /// Function for adding an item to a list
+    /// </summary>
+    /// <param name="value">Type of item value in the list</param>
+    public override void Add(T value)
+    {
+        if (Contains(value))
+        {
+            throw new RepeatValueException();
+        }
+
+        base.Add(value);
+    }
+
+    /// <summary>
+    /// Function to remove an item from the unique list
+    /// </summary>
+    /// <param name="index">Item position in the list</param>
+    public override bool RemoveAt(int index)
+    {
+        if (!base.RemoveAt(index))
+        {
+            throw new RemoveNonExistingElementException();
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Function to remove an item from the list
+    /// </summary>
+    /// <param name="value">Value to be deleted</param>
+    /// <returns>was the value in the list</returns>
+    public override bool Remove(T value)
+    {
+        if (!base.Remove(value))
+        {
+            throw new RemoveNonExistingElementException();
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Function for changing the value of an element by index
+    /// </summary>
+    /// <param name="index">Item position in the list</param>
+    /// <param name="value">New value</param>
+    public override bool ChangeElement(int index, T value)
+    {
+        if (index >= Size || index < 0)
+        {
+            return false;
+        }
+
+        if (base.GetItemByIndex(index).CompareTo(value) == 0)
+        {
+            return true;
+        }
+
+        if (Contains(value))
+        {
+            throw new InvalidOperationException();
+        }
+
+        base.ChangeElement(index, value);
+        return true;
+    }
+}
diff --git a/List/List/List/ListTest/ListTest.cs b/List/List/List/ListTest/ListTest.cs
new file mode 100644
index 0000000..88ef85f
--- /dev/null
+++ b/List/List/List/ListTest/ListTest.cs
@@ -0,0 +1,97 @@
+namespace ListTest;
+
+using NUnit.Framework;
+using List;
+using System;
+
+public class Tests
+{
+    private UniqueList<int> list = new();
+
+    [SetUp]
+    public void Setup()
+    {
+        list = new UniqueList<int>();
+    }
+
+    [Test]
+    public void ShouldExpectedZeroWhenListSizeEqualZero()
+    {
+        Assert.AreEqual(0, list.Size);
+    }
+
+    [Test]
+    public void ShouldSizeIncrementedWhenSizeAfterAddNonExisintgElement()
+    {
+        list.Add(1);
+        Assert.AreEqual(1, list.Size);
+    }
+
+    [Test]
+    public void ShouldThrowsRemoveNonExistingElementExceptionWhenRemoveFromEmptyList()
+    {
+        Assert.Throws<RemoveNonExistingElementException>(() => list.Remove(0));
+    }
+
+    [Test]
+    public void ShouldThrowsRemoveNonExistingElementExceptionWhenRemoveNonExistenElement()
+    {
+        list.Add(1);
+        list.Add(2);
+        list.Add(0);
+        list.Add(-12);
+        Assert.Throws<RemoveNonExistingElementException>(() => list.Remove(4));
+    }
+
+    [Test]
+    public void ShouldThrowsRepeatValueExceptionWhenAddExistingElement()
+    {
+        list.Add(1);
+        Assert.Throws<RepeatValueException>(() => list.Add(1));
+    }
+
+    [Test]
+    public void ShouldThrowsInvalidOperationExceptionWhenChandeElementWithExistingOne()
+    {
+        list.Add(1);
+        list.Add(2);
+        Assert.Throws<InvalidOperationException>(() => list.ChangeElement(0, 2));
+    }
+
+    [Test]
+    public void ShouldExpectedTrueWhenContainsForExistingElement()
+    {
+        list.Add(12);
+        Assert.AreEqual(true, list.Contains(12));
+    }
+
+    [Test]
+    public void ShouldExpectedFalseWhenContainsForExistingElement()
+    {
+        list.Add(2);
+        Assert.AreEqual(false, list.Contains(10));
+    }
+
+    [Test]
+    public void ShouldExpectedFalseWhenContainsForRemovedElement()
+    {
+        list.Add(2);
+        list.Remove(2);
+        Assert.AreEqual(false, list.Contains(2));
+    }
+
+    [Test]
+    public void ShouldExpectedFalseWhenChangeNonExistenElement()
+    {
+        Assert.AreEqual(false, list.ChangeElement(2, 12));
+    }
+
+    [Test]
+    public void ShouldExpectedFalseWhenContainsChangeReplacedElement()
+    {
+        list.Add(125);
+        list.ChangeElement(0, 12);
+        Assert.AreEqual(true, list.Contains(12));
+        Assert.AreEqual(false, list.Contains(125));
+    }
+}
\ No newline at end of file
diff --git a/List/List/List/ListTest/ListTest.csproj b/List/List/List/ListTest/ListTest.csproj
new file mode 100644
index 0000000..4cc12ed
--- /dev/null
+++ b/List/List/List/ListTest/ListTest.csproj
@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net6.0</TargetFramework>
+    <Nullable>enable</Nullable>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
+    <PackageReference Include="NUnit" Version="3.13.2" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.0.0" />
+    <PackageReference Include="coverlet.collector" Version="3.1.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\List\List.csproj" />
+  </ItemGroup>
+
+</Project>