Identify if the PDF Viewer has values in the Undo, Redo collections

5 Dec 20242 minutes to read

Syncfusion® Blazor PDF Viewer component allows you to identify if the PDF Viewer has values in the Undo and Redo collections using the CanUndo and CanRedo APIs of the PDF Viewer.

The following code example shows how to achieve this based on the Undo Redo actions.

@using Syncfusion.Blazor.PdfViewer
@using Syncfusion.Blazor.PdfViewerServer
@using Syncfusion.Blazor.Buttons

@if (canUndo)
{
    <button @onclick="undo">Undo</button>
}
else
{
    <button @onclick="undo" disabled>Undo</button>
}
@if (canRedo)
{
    <button @onclick="redo">Redo</button>
}
else
{
    <button @onclick="redo" disabled>Redo</button>
}
<SfPdfViewerServer @ref="@viewer"
                   @bind-CanUndo="@canUndo"
                   @bind-CanRedo="@canRedo"
                   DocumentPath="@DocumentPath"
                   Height="540px"
                   Width="100%">
</SfPdfViewerServer>

@code 
{
    SfPdfViewerServer viewer;
    bool canUndo = true;
    bool canRedo = true;
    private string DocumentPath { get; set; } = "wwwroot/Data/PDF_Succinctly.pdf";
    
    // Event triggers on Undo button click.
    private async Task undo()
    {
        // API to perform Undo action.
        await viewer.UndoAsync();
    }

    // Event triggers on Redo button click.
    private async Task redo()
    {
        // API to perform Redo action.
        await viewer.RedoAsync();
    }
}