DxFileInput.ExternalDropZoneDragOverCssClass Property

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

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v24.1.dll

NuGet Package: DevExpress.Blazor

Declaration

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

Property Value

Type	Description
String	CSS class names delimited by spaces.

Remarks

You can enable drag and drop functionality in the File Input component. To enable this functionality, create a drop zone and assign its CSS selector to the ExternalDropZoneCssSelector property. The ExternalDropZoneDragOverCssClass property specifies the CSS class applied to this drop zone when users drag files over it.

The following example implements a drop zone container for the File Input component:

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>
<DxFileInput
          Visible="@UploadVisible"
          ExternalSelectButtonCssSelector="#overviewDemoSelectButton"
          ExternalDropZoneCssSelector="#overviewDemoDropZone"
          ExternalDropZoneDragOverCssClass="custom-drop-zone-hover"
          MaxFileSize="15000000"
          FilesUploading="OnFilesUploading"
          SelectedFilesChanged="@SelectedFilesChanged">
</DxFileInput>

@code {
    bool UploadVisible { get; set; } = false;
    protected void SelectedFilesChanged(IEnumerable<UploadFileInfo> files) {
        UploadVisible = files.ToList().Count > 0;
        InvokeAsync(StateHasChanged);
    }
    protected async Task OnFilesUploading(FilesUploadingEventArgs args) {
        var file = args.Files[0];
        using var stream = new System.IO.MemoryStream();
        await file.OpenReadStream(file.Size).CopyToAsync(stream);
    }
}

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: File Input - 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.