pubic class ThemeHelper
{
    public ThemeHelper()
    {
        SystemEvents.UserPreferenceChanged += SystemEvents_UserPreferenceChanged;
    }

    private void SystemEvents_UserPreferenceChanged(object sender, UserPreferenceChangedEventArgs e)
    {
        switch (e.Category)
        {
            case UserPreferenceCategory.Accessibility:
                break;
            case UserPreferenceCategory.Color:
                break;
            case UserPreferenceCategory.Desktop:
                break;
            case UserPreferenceCategory.General:
                break;
            case UserPreferenceCategory.Icon:
                break;
            case UserPreferenceCategory.Keyboard:
                break;
            case UserPreferenceCategory.Menu:
                break;
            case UserPreferenceCategory.Mouse:
                break;
            case UserPreferenceCategory.Policy:
                break;
            case UserPreferenceCategory.Power:
                break;
            case UserPreferenceCategory.Screensaver:
                break;
            case UserPreferenceCategory.Window:
                break;
            case UserPreferenceCategory.Locale:
                break;
            case UserPreferenceCategory.VisualStyle:
                break;
        }
    }
}

    private const string RegistryKeyPathTheme = @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
    private const string RegSysMode = "SystemUsesLightTheme";

    public static UITheme GetWindowsTheme()
    {
        return GetThemeFromRegistry(RegSysMode);
    }

    private static UITheme GetThemeFromRegistry(string registryKey)
    {
        using var key = Registry.CurrentUser.OpenSubKey(RegistryKeyPathTheme);
        var themeValue = key?.GetValue(registryKey) as int?;
        return themeValue != 0 ? UITheme.Light : UITheme.Dark;
    }
    
    public enum UITheme
    {
        Light,
        Dark
    }

    public event EventHandler<FunctionEventArgs<UIWindowTheme>> WindowsThemeChanged;
    
    protected virtual void OnWindowsThemeChanged(UIWindowTheme theme)
    {
        EventHandler<FunctionEventArgs<UIWindowTheme>> handler = WindowsThemeChanged;
        handler?.Invoke(this, new FunctionEventArgs<UIWindowTheme>(theme));
    }

public class FunctionEventArgs<T> : RoutedEventArgs
{
    public FunctionEventArgs(T theme)
    {
        Theme = theme;
    }
    public FunctionEventArgs(RoutedEvent routedEvent, object source) : base(routedEvent, source) { }
    public T Theme { get; set; }
}

FunctionEventArgs<UIWindowTheme>

public class UIWindowTheme
{
    public Brush AccentBrush { get; set; }
    public UITheme CurrentTheme { get; set; }
}

case UserPreferenceCategory.General:
   var changedTheme = new UIWindowTheme()
   {
         AccentBrush = SystemParameters.WindowGlassBrush,
         CurrentTheme = GetWindowsTheme()
   };
   OnWindowsThemeChanged(changedTheme);
break;

    ThemeHelper tm = new ThemeHelper();
    tm.WindowsThemeChanged +=OnWindowsThemeChanged;

    private void OnWindowsThemeChanged(object? sender, FunctionEventArgs<RegistryThemeHelper.UIWindowTheme> e)
    {
        rec.Fill = e.Theme.AccentBrush;
        if (e.Theme.CurrentTheme == ThemeHelper.UITheme.Light)
        {
            Background = Brushes.White;
        }
        else
        {
            Background = Brushes.Black;
        }
    }

using System.ComponentModel.DataAnnotations;

namespace BlazorAsyncValidation.Shared;

public class UserDto
{
    [Required] public string Name { set; get; } = default!;
}

using BlazorAsyncValidation.Shared;
using Microsoft.AspNetCore.Mvc;

namespace BlazorAsyncValidation.Server.Controllers;

[ApiController, Route("api/[controller]/[action]")]
public class RegisterController : ControllerBase
{
    [HttpPost]
    public IActionResult IsUserNameUnique([FromBody] UserDto userModel)
    {
        if (string.Equals(userModel?.Name, "Vahid", StringComparison.OrdinalIgnoreCase))
        {
            return Ok(false);
        }

        return Ok(true);
    }
}

@page "/"

<PageTitle>Index</PageTitle>

<h2>Register</h2>

<EditForm EditContext="@EditContext" OnValidSubmit="DoSubmitAsync">
    <DataAnnotationsValidator/>
    <div class="row mb-2">
        <label class="col-form-label col-lg-2">Name:</label>
        <div class="col-lg-10">
            <InputText @bind-Value="Model.Name" class="form-control"/>
            <ValidationMessage For="@(() => Model.Name)"/>
        </div>
    </div>

    <button class="btn btn-secondary" type="submit">Submit</button>
</EditForm>

public partial class Index
{
    private const string UserValidationUrl = "/api/Register/IsUserNameUnique";

    private ValidationMessageStore? _messageStore;
    [Inject] private HttpClient HttpClient { set; get; } = default!;
    private EditContext? EditContext { set; get; }

    private UserDto Model { get; } = new();

    protected override void OnInitialized()
    {
        EditContext = new EditContext(Model);
        _messageStore = new ValidationMessageStore(EditContext);
        EditContext.OnFieldChanged += (sender, eventArgs) =>
        {
            var fieldIdentifier = eventArgs.FieldIdentifier;
            _messageStore?.Clear(fieldIdentifier);
            _ = InvokeAsync(async () =>
            {
                var errors = await OnValidateFieldAsync(fieldIdentifier.FieldName);
                if (errors?.Any() != true)
                {
                    return;
                }

                foreach (var error in errors)
                {
                    _messageStore?.Add(fieldIdentifier, error);
                }

                EditContext.NotifyValidationStateChanged();
            });
            StateHasChanged();
        };
        EditContext.OnValidationStateChanged += (sender, eventArgs) => StateHasChanged();
        EditContext.OnValidationRequested += (sender, eventArgs) => _messageStore?.Clear();
    }

    private async Task<IList<string>?> OnValidateFieldAsync(string fieldName)
    {
        switch (fieldName)
        {
            case nameof(UserDto.Name):
                var response = await HttpClient.PostAsJsonAsync(
                    UserValidationUrl,
                    new UserDto { Name = Model.Name });
                var responseContent = await response.Content.ReadAsStringAsync();
                if (string.Equals(responseContent, "false", StringComparison.OrdinalIgnoreCase))
                {
                    return new List<string>
                    {
                        $"`{Model.Name}` is in use. Please choose another name."
                    };
                }

                // TIP: It's better to use the `DntDebounceInputText` component for this case to reduce the network round-trips.

                break;
        }

        return null;
    }

dynamic excel = Activator.CreateInstance(Type.GetTypeFromProgID("Excel.Application", true));
excel.Visible = true;
Console.WriteLine("Press Enter to close Excel.");
Console.ReadLine();
excel.Quit();

 System.__ComObject does not contain a definition for 'Visible'

using Excel = Microsoft.Office.Interop.Excel;
// ...
var excel = new Excel.Application();
excel.Visible = true;
Console.WriteLine("Press Enter to close Excel.");
Console.ReadLine();
excel.Quit();

  <ItemGroup>
    <Reference Include="Interop.WIA">
      <HintPath>..\DNTScanner.Core.TypeLibrary\bin\Debug\Interop.WIA.dll</HintPath>
      <EmbedInteropTypes>True</EmbedInteropTypes>
    </Reference>
  </ItemGroup>

  <ItemGroup Condition=" '$(TargetFramework)' == 'net40' ">
    <Reference Include="Microsoft.CSharp" />
  </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
    <PackageReference Include="Microsoft.CSharp" Version="4.5.0" />
  </ItemGroup>

<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup>
  
  <!--
    The following 'COMReference' items were copied from a .NET Framework project.
    They were added by using the Visual Studio COM References window. 
    See https://docs.microsoft.com/en-us/visualstudio/ide/managing-references-in-a-project?view=vs-2017.
    Observe the 'EmbedInteropTypes' tag value.
    See https://docs.microsoft.com/en-us/visualstudio/msbuild/common-msbuild-project-items?view=vs-2017#comreference
  -->
  <ItemGroup>
    <COMReference Include="Microsoft.Office.Core">
      <Guid>{2DF8D04C-5BFA-101B-BDE5-00AA0044DE52}</Guid>
      <VersionMajor>2</VersionMajor>
      <VersionMinor>8</VersionMinor>
      <Lcid>0</Lcid>
      <WrapperTool>primary</WrapperTool>
      <Isolated>False</Isolated>
      <EmbedInteropTypes>True</EmbedInteropTypes>
    </COMReference>
    <COMReference Include="Microsoft.Office.Interop.Excel">
      <Guid>{00020813-0000-0000-C000-000000000046}</Guid>
      <VersionMajor>1</VersionMajor>
      <VersionMinor>9</VersionMinor>
      <Lcid>0</Lcid>
      <WrapperTool>primary</WrapperTool>
      <Isolated>False</Isolated>
      <EmbedInteropTypes>True</EmbedInteropTypes>
    </COMReference>
    <COMReference Include="VBIDE">
      <Guid>{0002E157-0000-0000-C000-000000000046}</Guid>
      <VersionMajor>5</VersionMajor>
      <VersionMinor>3</VersionMinor>
      <Lcid>0</Lcid>
      <WrapperTool>primary</WrapperTool>
      <Isolated>False</Isolated>
      <EmbedInteropTypes>True</EmbedInteropTypes>
    </COMReference>
  </ItemGroup>
</Project>

 return default (T);

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace PWS
{
    public static class Helpers
    {
        /// <summary>
        /// تغییر اندازه تصویر
        /// </summary>
        /// <param name="imageFile">آرایه بایتی از تصویر مورد نظر</param>
        /// <param name="targetSize">اندازه تصویر خروجی</param>
        /// <param name="format">فرمت تصویر خروجی</param>
        /// <returns></returns>
        public static byte[] ResizeImageFile(this byte[] imageFile, Int32 targetSize, ImageFormat format)
        {
            if (imageFile == null)
                throw new Exception("لطفا تصویر اصلی را مشخص نمایید");
            //باز کردن تصویر اصلی به عنوان یک جریان
            using (var oldImage = Image.FromStream(new MemoryStream(imageFile)))
            {
                //محاسبه اندازه تصویر خروجی با توجه به اندازه داده شده
                var newSize = CalculateDimensions(oldImage.Size, targetSize);
                //ایجاد تصویر جدید
                using (var newImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format24bppRgb))
                {
                    using (var canvas = Graphics.FromImage(newImage))
                    {
                        canvas.SmoothingMode = SmoothingMode.AntiAlias;
                        canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
                        canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
                        //تغییر اندازه تصویر اصلی و قرار دادن آن در تصویر جدید
                        canvas.DrawImage(oldImage, new Rectangle(new Point(0, 0), newSize));
                        var m = new MemoryStream();
                        //ذخیره تصویر جدید با فرمت وارد شده
                        newImage.Save(m, format);
                        return m.GetBuffer();
                    }
                }
            }
        }

        /// <summary>
        /// محاسبه ابعاد تصویر خروجی
        /// </summary>
        /// <param name="oldSize">اندازه تصویر اصلی</param>
        /// <param name="targetSize">اندازه تصویر خروجی</param>
        /// <returns></returns>
        private static Size CalculateDimensions(Size oldSize, Int32 targetSize)
        {
            var newSize = new Size();
            if (oldSize.Height > oldSize.Width)
            {
                newSize.Width = Convert.ToInt32(oldSize.Width * (targetSize / (float)oldSize.Height));
                newSize.Height = targetSize;
            }
            else
            {
                newSize.Width = targetSize;
                newSize.Height = Convert.ToInt32(oldSize.Height * (targetSize / (float)oldSize.Width));
            }
            return newSize;
        }
    }
}

byte[] oldImage = FileUploadImage.FileBytes;
byte[] target = oldImage.ResizeImageFile(100, ImageFormat.Jpeg);

    public class CustomImageTagProcessor : iTextSharp.tool.xml.html.Image
    {
        public override IList<IElement> End(IWorkerContext ctx, Tag tag, IList<IElement> currentContent)
        {
            IDictionary<string, string> attributes = tag.Attributes;
            string src;
            if (!attributes.TryGetValue(HTML.Attribute.SRC, out src))
                return new List<IElement>(1);

            if (string.IsNullOrEmpty(src))
                return new List<IElement>(1);

            if (src.StartsWith("data:image/", StringComparison.InvariantCultureIgnoreCase))
            {
                // data:[<MIME-type>][;charset=<encoding>][;base64],<data>
                var base64Data = src.Substring(src.IndexOf(",") + 1);
                var imagedata = Convert.FromBase64String(base64Data);
                var image = iTextSharp.text.Image.GetInstance(imagedata);

                var list = new List<IElement>();
                var htmlPipelineContext = GetHtmlPipelineContext(ctx);
                list.Add(GetCssAppliers().Apply(new Chunk((iTextSharp.text.Image)GetCssAppliers().Apply(image, tag, htmlPipelineContext), 0, 0, true), tag, htmlPipelineContext));
                return list;
            }
            else
            {
                return base.End(ctx, tag, currentContent);
            }
        }
    }

            using (var doc = new Document(PageSize.A4))
            {
                var writer = PdfWriter.GetInstance(doc, new FileStream("test.pdf", FileMode.Create));
                doc.Open();
                var html = @"<img src='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAD4AAABQCAMAAAB24TZcAAAABGdBTUEAANbY1E9YMgAAABl0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAGAUExURdSmeJp2SHlbQIRoSUg2J499a8KebqeHZuGufBEVJPz7+3NWPVxGMduwhPXEktnX1mtROLq7t5WDc2VMNv3LmKB8TMSidMbFxLGlmXlhSMSddpJUL+y8i3VlVqedlOzr6gUIF2lXRLCLY4ZyXLyYaYhtUYiJhJFyU1dBLLiVZnlwZrWRY/Hx8b+2rbySaJh9YqeooDw4NygnKvvJlpyblzksIUhGRryYckc7MPjGlKODX5x8VVA8K+azgM3FvDInHK2JW2ZbUOHh4Xt2cFpaWKeAUM6kel1RRJmUjo5vSrWzrJJ1WFhLQCQmMuK1iJiMgmthWPPCkOm3hEtBOunm5LCNXnJtZquEXmNkYvG+i7Ctq+y5hrWRbKqSeaN/WqmFVYFgQh8aGOa4isWkd8mcby4vONDNy0AwI5h2U19JMxkdLzIuL1JBMjQ3P5Z6Ve6/j93c2+Xi34KAfJ5/Xvj4+O/u7sSKVJd4Wo6QjXE+IeOwfQcNJoBeQ8Gdbf/Mmf///5GX6NEAAAcrSURBVHja3JbpX9pIGMchiWkgEaOBtaGinBLEyopFBeMqtYKI4kGt2lILFsUoXa3WdZcc/dd3JheHAvaz7/Z5Ec2Q7/yeaw7Lz/9klv8rfnM+Orz5cXLjZsL+67h9eCq9Vaxvzc6v3W6+/TX85kN6ixdokkQQCaE5vrg28Qv4a2yFQcpSi/HzH6efi+/UaEAwWAtepuvv3tw/B//hqZGQqDFSmyHC7v0z8EldlZQQEgTfMgF23h8/T+gEhQGrcQYrMBKVtvfDb4qU/j3DMK3SdIKWsNs++M1iS8R8W/gULyG1771w+/stQWpTpFpzByb09MRHEwaoxUxToGtaZiBrE72cXzMyhcDiIRgCHxJPIxKt5aF23gMf0iquz8BJmAAFpUStxvG0xIA3arcHPsvrJM1wvFTDeEGQeKCewCo1jgRDwKuJrrh9C3osIfyiz+NboZFKxU0xJEYmeJbBhPoKiKyMDXfHd0mJWSETnoKiKCmgSioFDKFr4T1lbn/fgkHf+PGu+A+A12imMqdAqzNUXlFCFP+gOD41CKJBcCB4bKSnOmitB5VWSgnMrSjhCnu8D1hoS1xP/KcH1BhZdGi4c4VNAh/I5PGyRjdQqje+A6YXPIpup/DhHlMUh44f1hAJ6x77z3OwVjG/0ml7Ot4gOWnxvkfbALw+2EnPGc43ojWk3qNt7hdpiSp0ajcMukHQPB/4o3vPf8TKQgc+pqXdkpEtgGewE7THel/j66dtdBLA1XAYRXK8AGbxC/6RHvjbCuOE0Kklk8lcg/+OicaJcOhfTflTVYCHuYvX3XH7QCxcUAol9i6VursLha+VfcLPHwamZjfSAgxi6QId6oFnC5awsjdoWYjFPrOlB3QONAtJjrwsetiq2jkzgfc9nPdklJBDyXvGj+Zf+jIKe7pPoNFoOHwyoyaQKFcD9z3wzbwSGnT6fCMB9u5UmWMLYwTJQo5QC2AB6r122ukBJeVWnA6HIwlLnp/bI/w5wI3tJR3LjcZMbvVzL/xHwOG+M6s2mFeSjRm0QRyDYnyCOEv/0fOYGM/vha4N3J1S5hoZhCAcYBro/AwV63NIjafuzL4rLSjOZYKeIT45j9XUnQTs/Y7Inbqp/pABeIPBqsTystr0/pd9T9jprZIGO9CHa4gTPHairxr/eP/rwai+YdzlWQfALSHu4qTxfHxiQKVTaBINvfCjDFo1Fmzjor/zP+0BNXdgxSTdqRe5w0bT2hq+293mdWDOSJ5DWbgwd4uGpSPxXW5WGzGddhYWHsDRguqpO5x9jjq4HY3BnjtcRRGGe/Xqn38YC6SraVt84jnXwo0FgC8kOK7s+mv91St6RhVnZ72Vqeln4EM+cFY43SHgdj584c9ormdFbx3Jbk73v9PuvNCCvx67ntPzlmG2xUvUhQpZz9roxHdwXx4e7Yb/fdXc7o81PFcUxW2ry+Wy5miM4gQkEAh0uxKfXWbdLXs1XGxZURRnXZpZrVbXegT/rUvm571itnncQPctWZso2hAdd61GIzIuf32y5zduL0VxtwQPWG2vB7QP0OKKVaejOI7L8lP4+S3r+wY+zSZfGPvGPlFlt8FQ3BCPQPYpfOjWs3QHtMVLJqmU0NLe9XVhsBpOwyER0+D1oE534t8Hsn/KctwLokxUgeunD6FwCA2xMGtAPAdhjkr55afwoaksGpHlAKTnWUK9ZIAt15k/U+mK5voSuoI9Vre/fZPOBcFQKg4+PXsXg7urVra0Stvqmud4mTp4hN/s+lAIy8ErIC7Oz8aITzqegYkUL4tawQ+ivEvudP7Gt6SPpCpewJ8BfN+pb/aq71dG2kjayLuJ3/vC+gB+EBe9Xm/8KEQs67hShMmgIRsNylFuFe9UL1IGHXHNAtr77ZYN7htNB8LxJmCnyaBZULpJ6/g4ZZQCX83FAS1u3675xnTaX/GKFdLl+gIaDZeFpU78rS9oDnzZEmHstqPJKc9n90LJPThyBUZIVRtMv8Q1v9Xx8bzxigddWo1t7yZ//zgSCwRiK6CO0PUD2OR4hMnhHfiPtYiJr4a8Jj4MbHNe7UC4RtTfc5wsd+DD6RbxxTZ8chtkrcJGIlqX41GqTVzFp3wmfmCNi5rNT74Z3nwHi2BjZW11AtdzgvxIfSBl4l/Klzr+bfLvzSNYA1u9xTfmz8f4lLmA5HWfgV8eTa7BEohxox1xeZ1F5Ef4fTrYnL4oGjb7QZ3JVgk2W4KJPMZvmWbo9KWJ27QsXKHm3DkhJT/Gs6z55lo0abV5wCSL5txL/CMa4PYPUXN+5qwTj68aXwa5MP4Efj/VDA4TW3BV3PQMp7Wlgnfg555mcPFO8RbXMbXv8Oh6pG3J7IRM8bq3Q/zKLFqUQ3GteNYvbepG1XG57O0Qt9Hmd1bOKC1qbZH/zbK78FWzYMJ2aZoXPq7kr8ZvORr+iUSjJzQb/Gpa5l8BBgBZTppAyfsf0wAAAABJRU5ErkJggg==' width='62' height='80' style='float: left; margin-right: 28px;' />";

                var tagProcessors = (DefaultTagProcessorFactory)Tags.GetHtmlTagProcessorFactory();
                tagProcessors.RemoveProcessor(HTML.Tag.IMG); // remove the default processor
                tagProcessors.AddProcessor(HTML.Tag.IMG, new CustomImageTagProcessor()); // use our new processor

                var cssResolver = new StyleAttrCSSResolver();
                cssResolver.AddCss(@"code { padding: 2px 4px; }", "utf-8", true);
                var charset = Encoding.UTF8;
                var hpc = new HtmlPipelineContext(new CssAppliersImpl(new XMLWorkerFontProvider()));
                hpc.SetAcceptUnknown(true).AutoBookmark(true).SetTagFactory(tagProcessors); // inject the tagProcessors
                var htmlPipeline = new HtmlPipeline(hpc, new PdfWriterPipeline(doc, writer));
                var pipeline = new CssResolverPipeline(cssResolver, htmlPipeline);
                var worker = new XMLWorker(pipeline, true);
                var xmlParser = new XMLParser(true, worker, charset);
                xmlParser.Parse(new StringReader(html));
            }
            Process.Start("test.pdf");