多个ComboBox绑定同一个数据源出现的问题解决办法

DataTable dt = new DataTable();
            dt = Common.XmlToDatatable(mPath, "常用四至");
            DataRow dr = dt.NewRow();
            dr["四至名称"] = "";//添加空行
            dt.Rows.InsertAt(dr, 0);
            
            cmbDZ.DataSource = dt.Copy();
            cmbDZ.DisplayMember = "四至名称";
            cmbNZ.DataSource = dt.Copy();
            cmbNZ.DisplayMember = "四至名称";
            cmbXZ.DataSource = dt.Copy();
            cmbXZ.DisplayMember = "四至名称";
            cmbBZ.DataSource = dt.Copy();
            cmbBZ.DisplayMember = "四至名称";