2025J v1 のアップデートでソートアイコンの形が変更になり、デフォルトで左側に表示されるようになりましたが、 そのソートアイコンを右側に表示するため、ShowSortPosition を「Right」に設定しても、適用されません。

Imports C1.Win.C1FlexGrid

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' FlexGridの設定
        C1FlexGrid1.AllowSorting = AllowSortingEnum.SingleColumn
        C1FlexGrid1.Glyphs(GlyphEnum.Ascending) = Image.FromFile("ascending.png")
        C1FlexGrid1.Glyphs(GlyphEnum.Descending) = Image.FromFile("descending.png")
        C1FlexGrid1.ShowSortPosition = ShowSortPositionEnum.Right  ' 有効にならない

        ' データの設定
        C1FlexGrid1(1, 1) = "A1"
        C1FlexGrid1(2, 1) = "A2"

        ' 回避方法
        C1FlexGrid1.ShowSort = False
        C1FlexGrid1.DrawMode = DrawModeEnum.OwnerDraw

    End Sub

    Private Sub C1FlexGrid1_OwnerDrawCell(sender As Object, e As OwnerDrawCellEventArgs) Handles C1FlexGrid1.OwnerDrawCell
        Dim grid As C1FlexGrid = CType(sender, C1FlexGrid)

        ' ヘッダセルのみ対象
        If e.Row = grid.Cols.Fixed Then
            ' デフォルト描画
            e.DrawCell()

            ' ソート中の列ならアイコンを右端に描画
            If grid.Cols(e.Col).Sort <> SortFlags.None Then
                Dim glyph As Image = Nothing

                If grid.Cols(e.Col).Sort = SortFlags.Ascending Then
                    glyph = grid.Glyphs(GlyphEnum.Ascending)
                ElseIf grid.Cols(e.Col).Sort = SortFlags.Descending Then
                    glyph = grid.Glyphs(GlyphEnum.Descending)
                End If

                If glyph IsNot Nothing Then
                    Dim rc As Rectangle = e.Bounds
                    Dim x As Integer = rc.Right - glyph.Width - 2  ' 右端に寄せる
                    Dim y As Integer = rc.Top + (rc.Height - glyph.Height) \ 2
                    e.Graphics.DrawImage(glyph, x, y, glyph.Width, glyph.Height)
                End If
            End If

            e.Handled = True  ' 独自描画を適用
        End If
    End Sub
End Class

using C1.Win.C1FlexGrid;

namespace prj_C1FlexGrid
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // FlexGridの設定
            c1FlexGrid1.AllowSorting = AllowSortingEnum.SingleColumn;
            c1FlexGrid1.Glyphs[GlyphEnum.Ascending] = Image.FromFile("ascending.png");
            c1FlexGrid1.Glyphs[GlyphEnum.Descending] = Image.FromFile("descending.png");
            c1FlexGrid1.ShowSortPosition = ShowSortPositionEnum.Right;  //有効にならない

            // データの設定
            c1FlexGrid1[1, 1] = "A1";
            c1FlexGrid1[2, 1] = "A2";

            // 回避方法
            c1FlexGrid1.ShowSort = false;
            c1FlexGrid1.DrawMode = DrawModeEnum.OwnerDraw;
        }

        private void c1FlexGrid1_OwnerDrawCell(object sender, OwnerDrawCellEventArgs e)
        {
            var grid = (C1FlexGrid)sender;

            // ヘッダセルのみ対象
            if (e.Row = grid.Cols.Fixed)
            {
                // デフォルト描画
                e.DrawCell();

                // ソート中の列ならアイコンを右端に描画
                if (grid.Cols[e.Col].Sort != SortFlags.None)
                {
                    Image glyph = null;
                    if (grid.Cols[e.Col].Sort == SortFlags.Ascending)
                        glyph = grid.Glyphs[GlyphEnum.Ascending];
                    else if (grid.Cols[e.Col].Sort == SortFlags.Descending)
                        glyph = grid.Glyphs[GlyphEnum.Descending];

                    if (glyph != null)
                    {
                        Rectangle rc = e.Bounds;
                        int x = rc.Right - glyph.Width - 2; // 右端に寄せる
                        int y = rc.Top + (rc.Height - glyph.Height) / 2;
                        e.Graphics.DrawImage(glyph, x, y, glyph.Width, glyph.Height);
                    }
                }

                e.Handled = true; // 独自描画を適用
            }
        }
    }
}