Code
public class ExcelToSQL
{
    //string SqlConnectionString = "Server=(local);Initial Catalog=Test;Integrated Security=True";
    public SqlConnection sqlcon;        //创建SQL连接
    public SqlCommand sqlcom;          //创建SQL命令对象

public ExcelToSQL()
    {
        DataOperation dataOperation = new DataOperation(); //用到平台的函数，就是初始化SqlConnection对象
        DBUnit dbUnit = dataOperation.GetDbUnit();
        sqlcon = (SqlConnection)dbUnit.cnt;
        if (sqlcon.State.ToString() == "Open")
            sqlcon.Close();
    }
    public int ImportSql(string excelPath, string tableName)  //导入的Excel的路径，数据库里的表名
    {
        if (!TableExist(tableName)) //表名是否存在
            return (int)ImportState.tableNameError;

DataTable dt = ExcelToDataTable(excelPath);
       if (dt == null)
        {
            return (int)ImportState.excelFormatError;
        }
        ArrayList tableField = GetTableField(tableName);   //表格的列名称

string columnName = "ID,"; //Excel里的列名，增加一个ID列
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            columnName += dt.Columns[i].ColumnName + ",";
            string currentColumn = dt.Columns[i].ToString().ToUpper(); //当前列名
            for (int j = 0; j < tableField.Count; j++)
            {
                if (tableField[j].ToString().ToUpper() == dt.Columns[i].ToString().ToUpper())
                    break;   //跳出本层和上一层循环，continue是跳出本层循环，如果用continue，会继续执行j++
                //Excel里的字段必须在Sql中都有
                if ((tableField[j].ToString().ToUpper() != dt.Columns[i].ToString().ToUpper()) && j == tableField.Count - 1)
                    return (int)ImportState.fieldMatchError;
            }
        }
        int m = columnName.LastIndexOf(',');
        columnName = columnName.Remove(m);  //移除最后一个逗号

sqlcom = new SqlCommand();
        sqlcom.Connection = sqlcon;
        sqlcon.Open();
        sqlcom.CommandType = CommandType.Text;

for (int h = 0; h < dt.Rows.Count; h++)
        {
            string value = "'" + System.Guid.NewGuid().ToString() + "'" + ",";
            for (int k = 0; k < dt.Columns.Count; k++) //根据列名得到值
            {
                value += "'" + dt.Rows[h][k].ToString() + "'" + ",";
            }
            value = value.Remove(0, 1);
            int n = value.LastIndexOf(',');
            value = value.Remove(n);    //移除最后一个逗号
            n = value.LastIndexOf("'");
            value = value.Remove(n);

try
            {
                string sql = "insert into " + tableName + "(" + columnName + ") values('" + value + "')";
                sqlcom.CommandText = sql;
                string sss = sqlcom.ExecuteNonQuery().ToString();
            }
            catch (Exception err)
            {
                string erroe = err.Message;
                return (int)ImportState.dataTypeError;
            }
        }
        sqlcon.Close();
        sqlcom.Dispose();

return (int)ImportState.right;
    }
    public DataTable ExcelToDataTable(string excelPath)  //把Excel里的数据转换为DataTable，并返回DataTable
    {
           string strCon = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + excelPath + ";Extended Properties='Excel 8.0;IMEX=1'";
        System.Data.OleDb.OleDbConnection Conn = new System.Data.OleDb.OleDbConnection(strCon);
        string strCom = "SELECT * FROM [Sheet1$]";
        DataTable dt;
        try
        {
            Conn.Open();
            System.Data.OleDb.OleDbDataAdapter myCommand = new System.Data.OleDb.OleDbDataAdapter(strCom, Conn);
            DataSet ds = new DataSet();
            myCommand.Fill(ds, "[Sheet1$]");
            Conn.Close();
            dt = ds.Tables[0];
        }
        catch(Exception err)
        {
            return null;
        }
        return dt;
    }
    public bool TableExist(string tableName) //查看数据库里是否有此表名
    {
        sqlcom = new SqlCommand();
        sqlcom.Connection = sqlcon;
        sqlcom.CommandType = CommandType.Text;
        try
        {
            sqlcon.Open();
            string sql = "select name from sysobjects where type='u'";
            sqlcom.CommandText = sql;
            SqlDataReader sqldr = sqlcom.ExecuteReader();
            while (sqldr.Read())
            {
                if (sqldr.GetString(0).ToUpper() == tableName.ToUpper())
                    return true;
            }
        }
        catch { return false; }
        finally
        {
            sqlcon.Close();
        }
        return false;
    }
    public ArrayList GetTableField(string tableName)  //得到数据库某一个表中的所有字段
    {
        ArrayList al = new ArrayList();
        sqlcom = new SqlCommand();
        sqlcom.Connection = sqlcon;
        sqlcom.CommandType = CommandType.Text;
        try
        {
            sqlcon.Open();
            string sql = "SELECT b.name FROM sysobjects a INNER JOIN syscolumns b ON a.id = b.id WHERE (a.name = '" + tableName + "')";
            sqlcom.CommandText = sql;
            SqlDataReader sqldr = sqlcom.ExecuteReader();
            while (sqldr.Read())
            {
                al.Add(sqldr.GetString(0));
            }
        }
        finally
        {
            sqlcon.Close();
        }
        return al; //返回的是表中的字段
    }
    public enum ImportState
    {
        right = 1, //成功
        tableNameError = 2,//表名不存在
        fieldMatchError = 3,//excel里的字段和数据库表里的字段不匹配
        dataTypeError = 4, //转换数据类型时发生错误
        excelFormatError=5,//Excel格式不能读取
    }
    public void Alert(string str)
    {
        HttpContext.Current.Response.Write("<script language='javascript'>alert('" + str + "');</script>");
    }
}

Code
 protected void btnExport_Click(object sender, EventArgs e)
    {
        string filepath = this.fileUpload.PostedFile.FileName;
        if (filepath != "")
        {
            if (this.txtTableName.Text != "")
            {
                if (filepath.Contains("xls"))
                {
                    int result = ets.ImportSql(filepath, this.txtTableName.Text);

if (result == (int)ExcelToSQL.ImportState.tableNameError)
                        ets.Alert("此表名在数据中不存在！");
                   else if(result==(int)ExcelToSQL.ImportState.excelFormatError)
                        ets.Alert("Excel格式不能正确读取！");
                    else if (result == (int)ExcelToSQL.ImportState.fieldMatchError)
                        ets.Alert("Excel里的字段和Sql Server里的字段不匹配！");
                    else if(result==(int)ExcelToSQL.ImportState.dataTypeError)
                        ets.Alert("转换数据类型时发生错误!");
                    else if (result == (int)ExcelToSQL.ImportState.right)
                    {
                        ets.Alert("导入成功");
                    }
                }
                else ets.Alert("上传的文件类型必须为excel文件！");
            }
            else ets.Alert("表名不能为空！");
        }
        else ets.Alert("没有选择要上传的文件！");
    }

Code
 <form id="form1" runat="server">
    <div>
        <asp:Label ID="Label1" runat="server" Text="路径"></asp:Label>
        &nbsp;<asp:FileUpload ID="fileUpload" runat="server" Width="443px" /><br />
        <asp:Label ID="Label2" runat="server" Text="数据库表名称"></asp:Label>&nbsp;
        <asp:TextBox ID="txtTableName" runat="server"></asp:TextBox><br />
        <asp:Button ID="btnExport" runat="server" Text="导入到SQL" OnClick="btnExport_Click" />
    </div>
    </form>