如何查找Listview / MVVM的子（Gridviewcolumn）

Question

在一个行为中（连接到windows.interactivity）我试图找到一个Listview的子项 - 特别是Gridviewcolumn-以便能够调整其宽度，代码是使用MVVM构建的，没有代码隐藏。

问题很简单，就是找不到使用Gridviewcolumn下面的代码，同时还有Maingrid的其他子代，f.e。一个按钮，没问题（参见下面的按钮示例）。

任何错误来自哪些建议？提前谢谢！

// _parent is the main Grid of the Window

Button button = GetTemplateChildByName(_parent); // for the button its working and the value is returned


GridViewColumn gridviewcolumn = GetTemplateChildByNames(_parent);// for the  GridViewColumn  its not working and no value is returned

....



  public Button GetTemplateChildByName(DependencyObject parent)
        {
            int childnum = VisualTreeHelper.GetChildrenCount(parent);
            for (int i = 0; i < childnum; i++)
            {
                var child = VisualTreeHelper.GetChild(parent, i);
                if (child is Button)
                {
                    return child as Button;
                }
                else
                {
                    var s = GetTemplateChildByName(child);
                    if (s != null)
                        return s;
                }
            }
            return null;
        }

     public GridViewColumn GetTemplateChildByNames(DependencyObject parent)
        {
            int childnum = VisualTreeHelper.GetChildrenCount(parent);
            for (int i = 0; i < childnum; i++)
            {
                var child = VisualTreeHelper.GetChild(parent, i);
                if (child is GridViewColumn)
                {
                    return child as GridViewColumn;
                }
                else
                {
                    var s = GetTemplateChildByNames(child);
                    if (s != null)
                        return s;
                }
            }
            return null;
        }