asp.net C# 导出EXCEL数据

if (dt == null)
{
return "";
}
Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();
if (xlApp == null)
{
return "无法创建Excel对象，可能您的机子未安装Excel";
}
Microsoft.Office.Interop.Excel.Workbooks workbooks = xlApp.Workbooks;
Microsoft.Office.Interop.Excel.Workbook workbook = workbooks.Add(Microsoft.Office.Interop.Excel.XlWBATemplate.xlWBATWorksheet);
Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[1];//取得Sheet1
Microsoft.Office.Interop.Excel.Range range;
long totalCount = dt.Rows.Count;

long rowRead = 0;
float percent = 0;

string[] ColumnList = columns.Split(new char[]{','},StringSplitOptions.RemoveEmptyEntries);
//写入字段
for (int i = 0; i < ColumnList.Length; i++)
{
worksheet.Cells[1, i + 1] = ColumnList[i];
range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[1, i + 1];
range.Interior.ColorIndex = 15;
range.Font.Bold = true;
}
//写入数值
for (int r = 0; r < dt.Rows.Count; r++)
{
for (int i = 0; i < dt.Columns.Count; i++)
{
worksheet.Cells[r + 2, i + 1] = dt.Rows[r][i];
}
rowRead++;
percent = ((float)(100 * rowRead)) / totalCount;
}
xlApp.Visible = true;