spectre.console/src/Spectre.Console/Borders/HorizontalBorder.cs

using System;

namespace Spectre.Console.Rendering
{
    /// <summary>
    /// Represents a horizontal border.
    /// </summary>
    public sealed class HorizontalBorder : Border
    {
        /// <inheritdoc/>
        protected override string GetBoxPart(BorderPart part)
        {
            return part switch
            {
                BorderPart.HeaderTopLeft => "─",
                BorderPart.HeaderTop => "─",
                BorderPart.HeaderTopSeparator => "─",
                BorderPart.HeaderTopRight => "─",
                BorderPart.HeaderLeft => " ",
                BorderPart.HeaderSeparator => " ",
                BorderPart.HeaderRight => " ",
                BorderPart.HeaderBottomLeft => "─",
                BorderPart.HeaderBottom => "─",
                BorderPart.HeaderBottomSeparator => "─",
                BorderPart.HeaderBottomRight => "─",
                BorderPart.CellLeft => " ",
                BorderPart.CellSeparator => " ",
                BorderPart.CellRight => " ",
                BorderPart.FooterBottomLeft => "─",
                BorderPart.FooterBottom => "─",
                BorderPart.FooterBottomSeparator => "─",
                BorderPart.FooterBottomRight => "─",
                _ => throw new InvalidOperationException("Unknown box part."),
            };
        }
    }
}