DxUpload.ExternalDropZoneDragOverCssClass Property

Assigns a CSS class to the drop zone when users drag files over it.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v25.1.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public string ExternalDropZoneDragOverCssClass { get; set; }

Property Value

Type	Description
String	CSS class names delimited by spaces.

Remarks

To enable drag and drop functionality in the Upload, implement an external zone where users can drop a file to upload. Use the ExternalDropZoneCssSelector property to specify the CSS selector of a container or HTML element. The ExternalDropZoneDragOverCssClass property defines the CSS class that is used for the drop zone when users drag files over it.

Razor

<div id="overviewDemoDropZone" class="card custom-drop-zone rounded-3 w-100 m-0">
    <span class="drop-file-icon mb-3"></span>
    <span class="drop-file-label">Drag and Drop File Here</span><span class="m-1">or</span>
    <DxButton Id="overviewDemoSelectButton"
              CssClass="m-1"
              RenderStyle="ButtonRenderStyle.Primary"
              Text="Select File" />
</div>
<DxUpload Name="myFile"
          Visible="@UploadVisible"
          ExternalSelectButtonCssSelector="#overviewDemoSelectButton"
          ExternalDropZoneCssSelector="#overviewDemoDropZone"
          ExternalDropZoneDragOverCssClass="custom-drop-zone-hover"
          MaxFileSize="15000000"
          UploadUrl="@GetUploadUrl("api/Upload/Upload/")"
          SelectedFilesChanged="@SelectedFilesChanged">
</DxUpload>

@code {
    bool UploadVisible { get; set; } = false;
    protected void SelectedFilesChanged(IEnumerable<UploadFileInfo> files) {
        UploadVisible = files.ToList().Count > 0;
        InvokeAsync(StateHasChanged);
    }
    protected string GetUploadUrl(string url) {
        return NavigationManager.ToAbsoluteUri(url).AbsoluteUri;
    }
}

CSS

.custom-drop-zone {
    padding: 0 !important;
    border-style: dashed;
    border-width: 2px !important;
    height: 230px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background-color: rgba(183, 183, 183, 0.1);
}
.custom-drop-zone.custom-drop-zone-hover {
    border-style: solid;
}

Run Demo: Upload - Overview

For more information on how to apply CSS classes to DevExpress Blazor components, refer to the following help topic: CSS Classes.

If your custom CSS ruleset includes only one class selector, some property declarations can be ignored. DevExpress themes can apply predefined CSS rules that are more specific and have higher priority than a single-selector rule. Make your rule more specific to increase the priority of your ruleset. See the following help topic for an example: Apply Styles to Components. For more information about how a browser calculates rule priority, refer to the following topic: Understanding the cascade.

You can use the !important flag to override other CSS rules. However, note that this flag modifies the standard behavior of the cascade, which can make troubleshooting CSS issues quite challenging, particularly in large stylesheets.

To limit the scope of CSS styles so that they only apply to a specific component and do not accidentally affect other parts of the application, use Blazor CSS isolation. This feature allows you to define CSS styles that apply only to HTML elements rendered by a specific Blazor component.