C#添加word中shape文本无法居中

文本水平居中无效果，一直是左对齐

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using MSWord = Word;
using System.IO;
using System.Reflection;

MSWord.Shape WBK1 = wordDoc.Shapes.AddTextbox(Office.MsoTextOrientation.msoTextOrientationHorizontal, left, top, width, height);

        WBK1.TextFrame.TextRange.Text = "12316546";
        WBK1.TextFrame.HorizontalAnchor = Office.MsoHorizontalAnchor.msoAnchorCenter;
        WBK1.TextFrame.VerticalAnchor = Office.MsoVerticalAnchor.msoAnchorMiddle;

运行结果及报错内容

我的解答思路和尝试过的方法

尝试了其他格式，水平文本无法调整格式

我想要达到的结果

水平文本居中