Добавьте файлы проекта.

Base64encoder.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.32126.317
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Base64encoder", "Base64encoder\Base64encoder.csproj", "{CA02C7C7-9449-4F15-A6C8-886918B02356}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Base64encoderTests", "Base64encoderTests\Base64encoderTests.csproj", "{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Debug|x64 = Debug|x64
+		Release|Any CPU = Release|Any CPU
+		Release|x64 = Release|x64
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Debug|x64.ActiveCfg = Debug|x64
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Debug|x64.Build.0 = Debug|x64
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Release|Any CPU.Build.0 = Release|Any CPU
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Release|x64.ActiveCfg = Release|x64
+		{CA02C7C7-9449-4F15-A6C8-886918B02356}.Release|x64.Build.0 = Release|x64
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Debug|x64.Build.0 = Debug|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Release|x64.ActiveCfg = Release|Any CPU
+		{A95BADAC-7AC8-4D7A-ACA8-6ABE9BAEA94E}.Release|x64.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		VisualSVNWorkingCopyRoot = .
+		SolutionGuid = {12CCE259-8107-43EB-8F2E-526B3D47F8A4}
+	EndGlobalSection
+EndGlobal

Base64encoder/Base64encoder.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+    <RootNamespace>Ru.Pfr.Crypto.Base64encoder</RootNamespace>
+    <Platforms>AnyCPU;x64</Platforms>
+    <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+</Project>

Base64encoder/Encoder64.cs

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+using System;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Ru.Pfr.Crypto.Base64encoder
+{
+    public static class Encoder64
+    {
+        public static String EncodeTo64(String _string)
+        {
+            string result;
+            try
+            {
+                SHA1Managed hasher = new();
+                byte[] pwdBytes = Encoding.Default.GetBytes(_string);                
+                byte[] keyBytes = hasher.ComputeHash(pwdBytes);
+                hasher.Dispose();
+                result = Convert.ToBase64String(keyBytes);
+            }
+            catch (Exception ex)
+            {
+                throw new Exception(ex.Message, ex);
+            }
+            return result;
+        }
+    }
+}

Base64encoderTests/Base64encoderTests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>.NETCoreApp,Version=v5.0</TargetFramework>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="2.2.7" />
+    <PackageReference Include="MSTest.TestFramework" Version="2.2.7" />
+    <PackageReference Include="coverlet.collector" Version="3.1.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Base64encoder\Base64encoder.csproj" />
+  </ItemGroup>
+
+</Project>

Base64encoderTests/Encoder64Tests.cs

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+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Ru.Pfr.Crypto.Base64encoder;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Ru.Pfr.Crypto.Base64encoder.Tests
+{
+    [TestClass()]
+    public class Encoder64Tests
+    {
+        [TestMethod()]
+        public void EncodeTo64Test()
+        {
+            String result = Encoder64.EncodeTo64("MyPassword");
+            Console.WriteLine(result);
+            
+        }
+    }
+}