Add project files.

LTWindows.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.4.33110.190
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "LTWindows", "LTWindows\LTWindows.csproj", "{082D1086-846A-4D1E-8DBC-08BA8DAD2B99}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{082D1086-846A-4D1E-8DBC-08BA8DAD2B99}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{082D1086-846A-4D1E-8DBC-08BA8DAD2B99}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{082D1086-846A-4D1E-8DBC-08BA8DAD2B99}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{082D1086-846A-4D1E-8DBC-08BA8DAD2B99}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {46D3B702-0E82-438F-AE3A-FF2A3E34584B}
+	EndGlobalSection
+EndGlobal

LTWindows/Core/InputManager.cs

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+namespace LTWindows.Core
+{
+    internal class InputManager
+    {
+        public static void txtb_KeyPress(ref object sender, ref KeyPressEventArgs e)
+        {
+            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
+                 e.KeyChar != '-')
+            {
+                e.Handled = true;
+            }
+
+            // Only allow one minus
+            if (e.KeyChar == '-' && ((TextBox)sender).Text.IndexOf('-') > -1)
+            {
+                e.Handled = true;
+            }
+        }
+    }
+}

LTWindows/Core/Matrix.cs

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+namespace LTWindows.Core
+{
+	internal class Matrix
+	{
+		public int[,] matrix { get; set; }
+		public int SoDong { get; }
+		public int SoCot { get; }
+
+		public bool isSquare { get => SoCot == SoDong; }
+
+		public Matrix(int SoCot, int SoDong)
+		{
+			try
+			{
+				this.SoDong = SoDong;
+				this.SoCot = SoCot;
+				matrix = new int[SoDong, SoCot];
+			}
+			catch (Exception e)
+			{
+				MessageBox.Show(e.Message);
+			}
+		}
+
+		public int TotalDiagonalRightToLeft(Matrix a)
+		{
+			int result = 0;
+
+			for (int i = 0; i < a.SoDong; i++)
+			{
+				result += a.matrix[i, i];
+			}
+
+			return result;
+		}
+
+		public int TotalDiagonalLeftToRight(Matrix a)
+		{
+			int result = 0;
+
+			for (int i = 0; i < a.SoDong; i++)
+			{
+				int j = a.SoCot - i - 1;
+				result += a.matrix[i, j];
+			}
+
+			return result;
+		}
+
+		public Matrix Multiplication(Matrix a, Matrix b)
+		{
+			if (a.SoDong != b.SoCot)
+			{
+				MessageBox.Show("");
+				return new Matrix(0, 0);
+			}
+
+			Matrix result = new(a.SoDong, b.SoCot);
+
+			for (int i = 0; i < result.SoDong; i++)
+			{
+				for (int j = 0; j < result.SoCot; j++)
+				{
+					result.matrix[i, j] = 0;
+					for (int r = 0; r < a.SoDong; r++)
+					{
+						result.matrix[i, j] += a.matrix[i, r] * b.matrix[r, j];
+					}
+				}
+			}
+
+			return result;
+		}
+
+	}
+}

LTWindows/Core/Number.cs

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+namespace LTWindows.Core
+{
+    internal class Number
+    {
+        public static bool isEven(long a)
+        {
+            return (a & 1) == 0;
+        }
+
+        public static bool isOdd(long a)
+        {
+            return !isEven(a);
+        }
+
+        public static bool isPositive(long a)
+        {
+            return a > 0;
+        }
+
+        public static bool isNegative(long a)
+        {
+            return a < 0;
+        }
+
+        public static bool isPrimeNumber(long a)
+        {
+            if (a < 2)
+            {
+                return false;
+            }
+
+            if (a == 2)
+            {
+                return true;
+            }
+
+            if (a % 2 == 0)
+            {
+                return false;
+            }
+
+            for (long i = 3; i <= Math.Sqrt(a); i += 2)
+            {
+                if (a % i == 0)
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        public static ulong TotalDivisor(long a)
+        {
+            ulong result = 0;
+            for (long i = 1; i <= a; i++)
+            {
+                if (a % i == 0)
+                {
+                    result += (ulong)i;
+                }
+            }
+            return result;
+        }
+
+        public static bool isPerfectNumber(long a)
+        {
+            if ((ulong)(2 * a) == TotalDivisor(a))
+            {
+                return true;
+            }
+            return false;
+        }
+
+        public static bool isFibonacciNumber(long a)
+        {
+            long Fib1 = 1;
+            long Fib2 = 1;
+            long Fib = 1;
+            while (Fib < a)
+            {
+                Fib = Fib1 + Fib2;
+                Fib1 = Fib2;
+                Fib2 = Fib;
+            }
+            if (Fib == a) return true;
+            return false;
+        }
+    }
+}

LTWindows/Core/PhanSo.cs

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+using System.Numerics;
+
+namespace LTWindows.Core
+{
+    internal class PhanSo
+    {
+        private int Mau;
+
+        public PhanSo()
+        {
+            TuSo = 0;
+            Mau = 1;
+        }
+
+        public PhanSo(int Tu, int Mau)
+        {
+            TuSo = Tu;
+            this.Mau = Mau;
+        }
+
+        public int MauSo
+        {
+            get => Mau;
+            set => Mau = value;
+        }
+
+        public int TuSo { get; set; }
+
+        public PhanSo RutGon(PhanSo a)
+        {
+            int _gcd = (int)BigInteger.GreatestCommonDivisor(a.TuSo, a.MauSo);
+            a.TuSo /= _gcd;
+            a.MauSo /= _gcd;
+            return a;
+        }
+
+        public PhanSo Tong(PhanSo a, PhanSo b)
+        {
+            PhanSo result = new();
+
+            if (a.MauSo == b.MauSo)
+            {
+                result.TuSo = a.TuSo + b.TuSo;
+                result.MauSo = a.MauSo;
+                return RutGon(result);
+            }
+
+            result.TuSo = a.TuSo * b.MauSo + b.TuSo * a.MauSo;
+            result.MauSo = a.MauSo * b.MauSo;
+            return RutGon(result);
+        }
+
+        public PhanSo Hieu(PhanSo a, PhanSo b)
+        {
+            PhanSo result = new();
+
+            if (a.MauSo == b.MauSo)
+            {
+                result.TuSo = a.TuSo + -b.TuSo;
+                result.MauSo = a.MauSo;
+                return RutGon(result);
+            }
+
+            result.TuSo = a.TuSo * b.MauSo - b.TuSo * a.MauSo;
+            result.MauSo = a.MauSo * b.MauSo;
+            return RutGon(result);
+        }
+
+        public PhanSo Tich(PhanSo a, PhanSo b)
+        {
+            PhanSo result = new();
+            result.TuSo = a.TuSo * b.TuSo;
+            result.MauSo = a.MauSo * b.MauSo;
+            return RutGon(result);
+        }
+
+        public PhanSo Thuong(PhanSo a, PhanSo b)
+        {
+            PhanSo result = new();
+            result.TuSo = a.TuSo * b.MauSo;
+            result.MauSo = a.MauSo * b.TuSo;
+            return RutGon(result);
+        }
+    }
+}

LTWindows/LTWindows.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net6.0-windows</TargetFramework>
+    <Nullable>enable</Nullable>
+    <UseWindowsForms>true</UseWindowsForms>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Update="Properties\Resources.Designer.cs">
+      <DesignTime>True</DesignTime>
+      <AutoGen>True</AutoGen>
+      <DependentUpon>Resources.resx</DependentUpon>
+    </Compile>
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Update="Properties\Resources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>Resources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
+  </ItemGroup>
+
+</Project>