spectre.console/src/Spectre.Console/Rendering/Borders/Tables/RoundedTableBorder.cs

using System;

namespace Spectre.Console.Rendering
{
    /// <summary>
    /// Represents a rounded border.
    /// </summary>
    public sealed class RoundedTableBorder : TableBorder
    {
        /// <inheritdoc/>
        public override TableBorder? SafeBorder => TableBorder.Square;

        /// <inheritdoc/>
        public override string GetPart(TableBorderPart part)
        {
            return part switch
            {
                TableBorderPart.HeaderTopLeft => "╭",
                TableBorderPart.HeaderTop => "─",
                TableBorderPart.HeaderTopSeparator => "┬",
                TableBorderPart.HeaderTopRight => "╮",
                TableBorderPart.HeaderLeft => "│",
                TableBorderPart.HeaderSeparator => "│",
                TableBorderPart.HeaderRight => "│",
                TableBorderPart.HeaderBottomLeft => "├",
                TableBorderPart.HeaderBottom => "─",
                TableBorderPart.HeaderBottomSeparator => "┼",
                TableBorderPart.HeaderBottomRight => "┤",
                TableBorderPart.CellLeft => "│",
                TableBorderPart.CellSeparator => "│",
                TableBorderPart.CellRight => "│",
                TableBorderPart.FooterTopLeft => "├",
                TableBorderPart.FooterTop => "─",
                TableBorderPart.FooterTopSeparator => "┼",
                TableBorderPart.FooterTopRight => "┤",
                TableBorderPart.FooterBottomLeft => "╰",
                TableBorderPart.FooterBottom => "─",
                TableBorderPart.FooterBottomSeparator => "┴",
                TableBorderPart.FooterBottomRight => "╯",
                _ => throw new InvalidOperationException("Unknown border part."),
            };
        }
    }
}