使用DevExpress.XtraReports.UI.XtraReport 设计报表的时候如何格式化字符串

DataTable dt = new DataTable();
dt = _dt;
Report.DataSource = dt;

XRBinding binding;
binding = new XRBinding("Text", DataSource, "a.field1");
xlable1.DataBindings.Add(binding);
binding = new XRBinding("Text", DataSource, "a.field2");
xlable2.DataBindings.Add(binding);
binding = new XRBinding("Text", DataSource, "a.ym_pc");
xlable3.DataBindings.Add(binding);
binding = new XRBinding("Text", DataSource, "a.st_se");
binding.FormatString = "{0:n2}";//把这个里面的数据格式化为  123,123,123。23这种格式
xlable4.DataBindings.Add(binding);

binding = new XRBinding("Text", DataSource, "a.xmType");
xrTableCell5.DataBindings.Add(binding);
binding = new XRBinding("Text", DataSource, "a.fenleiSE");
binding.FormatString = "{0:n2}";
xrTableCell7.DataBindings.Add(binding);

GroupField groupField2 = new GroupField("xmType");
GroupHeader2.GroupFields.Add(groupField2);

binding = new XRBinding("Text", DataSource, "a.field");
xlable5.DataBindings.Add(binding);
binding = new XRBinding("Text", DataSource, "a.fieldSE");
binding.FormatString = "{0:n2}";
xlable6.DataBindings.Add(binding);

GroupField groupField = new GroupField("field");
GroupHeader1.GroupFields.Add(groupField);