A Blazor component to create panes separated by a slidable splitter bar.

• Live Demo

Note
I know the same feature component library, the "BlazorSliders", already exists, but it was a bit unsmooth, particularly on Blazor Server apps. So I've decided to create another one on my hand.

1. Add package to your project like this.

dotnet add package Toolbelt.Blazor.SplitContainer

3. Open Toolbelt.Blazor.Splitter namespace in _Imports.razor file.

@* This is "_Imports.razor" *@
...
@using Toolbelt.Blazor.Splitter

4. Then you can use the SplitContainer component in your Blazor app.

<SplitContainer @bind-FirstPaneSize="_PaneSize">

    <FirstPane>
        <h1>Hello</h1>
    </FirstPane>

    <SecondPane>
        <h1>World</h1>
    </SecondPane>

</SplitContainer>

@code {
    private int _PaneSize = 80;
}

Warning
You can specify the pane size to only either the FirstPaneSize or the SecondPaneSize parameter. If you specify both the FirstPaneSize or the SecondPaneSize parameters, then the splitter won't work.

The Orientation parameter represents the "Splitter Bar" orientation that splits the SplitContainer's client area into two panes. The following figures show the layout you will see with each SplitterOrientation enum value set to the Orientation parameter.

Vertical	Horizontal

When you set the FirstPaneSize parameter, the first pane will be fixed size, and the second pane will be stretched to fill the remaining area of the SplitContainer.

On the other hand, when you set the SecondPaneSize parameter, the first pane will be stretched to fill the remaining area of the SplitContainer, and the second pane will be fixed size.

⚠️ Warning

I strongly recommend binding a pane size parameter to a field variable, like the following example.

<SplitContainer @bind-FirstPaneSize="_PaneSize">
    ...
</SplitContainer>

@code {
    private int _PaneSize = 80;
}

When you set a pane size parameter with a literal value, like below,

<SplitContainer FirstPaneSize="80">
    ...
</SplitContainer>

the pane size might be reset unintendedly to that literal value you specified even after a user has operated to resize the pane.

Please refer to the following example if you want to save and restore the pane size. The following example shows you how to save and restore the pane size into a web browser's local storage (The example uses the Blazored.LocalStorage NuGet package to access the web browser's local storage API).

@inject ILocalStorageService LocalStorage

<SplitContainer @bind-FirstPaneSize="_PaneSize"
                @bind-FirstPaneSize:after="OnPaneSizeChanged">
    ...
</SplitContainer>

@code {
  private int _PaneSize = 80;

  protected override async Task OnAfterRenderAsync(bool firstRender)
  {
    if (firstRender)
    {
      var paneSizeStr = await this.LocalStorage.GetItemAsStringAsync("_PaneSize");
      if (int.TryParse(paneSizeStr, out var paneSize)) this._PaneSize = paneSize;
      this.StateHasChanged();
    }
  }

  private async Task OnPaneSizeChanged()
  {
    await this.LocalStorage.SetItemAsStringAsync("_PaneSize", _PaneSize.ToString());
  }
}

The size of the splitter bar is defined by the CSS custom property named --splitter-bar-size scoped in the split-container CSS class (The default value is '4px'). So you can change the size of the splitter bar by overriding that CSS custom property value like the following example.

::deep .split-container {
    --splitter-bar-size: 14px;
}

Release notes

Mozilla Public License Version 2.0