How to prevent uploading or removing files in Uploader component

4 Nov 20251 minute to read

Prevent selected files from being uploaded and block removal when the remove button is clicked by handling Uploader events. The BeforeUpload event fires before the upload begins and can be used to cancel the operation or add custom parameters. The BeforeRemove event fires when a file is about to be removed and can be used to cancel removal (for example, after confirming with the user).

With server-side API endpoint

@using Syncfusion.Blazor.Inputs
<SfUploader AutoUpload="false">
    <UploaderAsyncSettings SaveUrl="https://blazor.syncfusion.com/services/production/api/FileUploader/Save"
                           RemoveUrl="https://blazor.syncfusion.com/services/production/api/FileUploader/Remove"></UploaderAsyncSettings>
    <UploaderEvents BeforeUpload="@BeforeUploadHandler" BeforeRemove="@BeforeRemovehandler"></UploaderEvents>
</SfUploader>
@code {
    private void BeforeUploadHandler(BeforeUploadEventArgs args)
    {
        // You can prevent uploading by setting "Cancel" to true.
        args.Cancel =  true;
    }
    private void BeforeRemovehandler(BeforeRemoveEventArgs args)
    {
        // You can prevent removing by setting "Cancel" to true.
        args.Cancel =  true;
    }
}

Without server-side API endpoint

@using Syncfusion.Blazor.Inputs
<SfUploader AutoUpload="false">
    <UploaderEvents BeforeUpload="@BeforeUploadHandler" BeforeRemove="@BeforeRemovehandler"></UploaderEvents>
</SfUploader>
@code {
    private void BeforeUploadHandler(BeforeUploadEventArgs args)
    {
        // You can prevent uploading by setting "Cancel" to true.
        args.Cancel =  true;
    }
    private void BeforeRemovehandler(BeforeRemoveEventArgs args)
    {
        // You can prevent removing by setting "Cancel" to true.
        args.Cancel =  true;
    }
}