添加项目文件。

App.config

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+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+    <startup> 
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.8" />
+    </startup>
+</configuration>

Json.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.Serialization.Json;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SteamGuardDesktop
+{
+    public class Json
+    {
+        public static T parse<T>(string jsonString)
+        {
+            using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString)))
+            {
+                return (T)new DataContractJsonSerializer(typeof(T)).ReadObject(ms);
+            }
+        }
+        public static string stringify(object jsonObject)
+        {
+            using (var ms = new MemoryStream())
+            {
+                new DataContractJsonSerializer(jsonObject.GetType()).WriteObject(ms, jsonObject);
+                return Encoding.UTF8.GetString(ms.ToArray());
+            }
+        }
+    }
+}

MainForm.cs

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+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Data;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+
+namespace SteamGuardDesktop
+{
+    public partial class MainForm : Form
+    {
+        public MainForm()
+        {
+            InitializeComponent();
+        }
+
+        private string code = string.Empty;
+        private SharedSecret secret = new SharedSecret();
+
+        private void timer1_Tick(object sender, EventArgs e)
+        {
+            long timestamp = Utils.GetSystemUnixTime();
+            int timeLeft = 30 - (int)(Math.Floor((decimal)timestamp) % 30);
+            this.progressBar1.Value = timeLeft;
+            if (timeLeft < 5)
+            {
+                progressBar1.setColor(Brushes.Red);
+            }else if (timeLeft < 10)
+            {
+                progressBar1.setColor(Brushes.Orange);
+            }
+            else if (timeLeft == 30)
+            {
+                RefreshCode();
+                progressBar1.setColor(Brushes.LimeGreen);
+            }
+        }
+
+        private void MainForm_Load(object sender, EventArgs e)
+        {
+            Initialize(sender, e);
+        }
+
+        private void Initialize(object sender, EventArgs e)
+        {
+            // Check the file
+
+            if (!File.Exists("config.json"))
+            {
+                label1.Text = "Config first!";
+                timer1.Enabled = false;
+                Utils.FileWrite(Application.StartupPath + "\\config.json", Json.stringify(new SharedSecret()));
+                return;
+            }
+
+            // Check whether the code is valid
+
+            secret = Json.parse<SharedSecret>(Utils.FileRead(Application.StartupPath + "\\config.json"));
+            string code = string.Empty;
+            long timestamp = Utils.GetSystemUnixTime();
+            try
+            {
+                code = SteamAuth.GenerateSteamGuardCodeForTime(secret.SharedSecretString, timestamp);
+            }
+            catch (Exception)
+            {
+                code = "Secret invalid!";
+                this.label1.Text = code;
+                timer1.Enabled = false;
+                progressBar1.Value = 0;
+                return;
+            }
+
+            // All the data check passed
+            RefreshCode();
+            timer1_Tick(sender, e);
+        }
+
+        private void RefreshCode()
+        {
+            long timestamp = Utils.GetSystemUnixTime();
+            code = SteamAuth.GenerateSteamGuardCodeForTime(secret.SharedSecretString, timestamp);
+            this.label1.Text = code;
+        }
+    }
+}

MainForm.resx

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+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+    
+    Version 2.0
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+    
+    Example:
+    
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+                
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+    
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <metadata name="timer1.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
+    <value>17, 17</value>
+  </metadata>
+</root>

Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+
+namespace SteamGuardDesktop
+{
+    static class Program
+    {
+        /// <summary>
+        /// 应用程序的主入口点。
+        /// </summary>
+        [STAThread]
+        static void Main()
+        {
+            Application.EnableVisualStyles();
+            Application.SetCompatibleTextRenderingDefault(false);
+            Application.Run(new MainForm());
+        }
+    }
+}