使用ADO.NET将数据导出到Excel并提供下载

public string DataTableToExcel(DataTable dt,string excelPath)
{
if(dt == null)
{
return "DataTable不能为空";
}

int rows = dt.Rows.Count;
int cols = dt.Columns.Count;
StringBuilder sb;
string connString;

if(rows == 0)
{
return "没有数据";
}

sb = new StringBuilder();
connString = string.Format(ConnectionString,excelPath);

//生成创建表的脚本
sb.Append("CREATE TABLE ");
sb.Append(dt.TableName + " ( ");

for(int i=0;i<cols;i++)
{
if(i < cols - 1)
sb.Append(string.Format("{0} varchar,",dt.Columns.ColumnName));
else
sb.Append(string.Format("{0} varchar)",dt.Columns.ColumnName));
}

using(OleDbConnection objConn = new OleDbConnection(connString))
{
OleDbCommand objCmd = new OleDbCommand();
objCmd.Connection = objConn;

objCmd.CommandText = sb.ToString();

try
{
objConn.Open();
objCmd.ExecuteNonQuery();
}
catch(Exception e)
{
return "在Excel中创建表失败，错误信息：" + e.Message;
}

生成插入数据脚本#region 生成插入数据脚本
sb.Remove(0,sb.Length);
sb.Append("INSERT INTO ");
sb.Append(dt.TableName + " ( ");

for(int i=0;i<cols;i++)
{
if(i < cols - 1)
sb.Append(dt.Columns.ColumnName + ",");
else
sb.Append(dt.Columns.ColumnName + ") values (");
}

for(int i=0;i<cols;i++)
{
if(i < cols - 1)
sb.Append("@" + dt.Columns.ColumnName + ",");
else
sb.Append("@" + dt.Columns.ColumnName + ")");
}
#endregion


//建立插入动作的Command
objCmd.CommandText = sb.ToString();
OleDbParameterCollection param = objCmd.Parameters;

for(int i=0;i<cols;i++)
{
param.Add(new OleDbParameter("@" + dt.Columns.ColumnName, OleDbType.VarChar));
}

//遍历DataTable将数据插入新建的Excel文件中
foreach (DataRow row in dt.Rows)
{
for (int i=0; i<param.Count; i++)
{
param.Value = row;
}

objCmd.ExecuteNonQuery();
}

return "数据已成功导入Excel";
}//end using
}