SqlParameter的感悟

1.在更新DataTable或是DataSet时，如果不采用SqlParameter，那么当输入的Sql语句出现歧义时，如字符串中含有单引号，程序就会发生错误，并且他人可以轻易地通过拼接Sql语句来进行注入攻击。

2.

string sql = "update Table1 set name = 'Pudding' where ID = '1'";//未采用SqlParameter
SqlConnection conn = new SqlConnection();
conn.ConnectionString = "Data Source=.\\SQLExpress;Integrated Security=true;AttachDbFilename=|DataDirectory|\\Database.mdf;User Instance=true";//连接字符串与数据库有关
SqlCommand cmd = new SqlCommand(sql, conn);
try
{
    conn.Open();
    return(cmd.ExecuteNonQuery());
}
catch (Exception)
{
    return -1;
    throw;
}
finally
{
    conn.Close();
}

//单个添加

SqlParameter sp = new SqlParameter("@name", "Pudding");
cmd.Parameters.Add(sp);
sp = new SqlParameter("@ID", "1");
cmd.Parameters.Add(sp);

//批量查询
SqlParameter[] paras = new SqlParameter[] { new SqlParameter("@name", "Pudding"), new SqlParameter("@ID", "1") };
cmd.Parameters.AddRange(paras);

//通过SqlParameter向数据库存储及读取图片的代码。

public int SavePhoto(string photourl)
{
    FileStream fs = new FileStream(photourl, FileMode.Open, FileAccess.Read);//创建FileStream对象，用于向BinaryReader写入字节数据流
    BinaryReader br = new BinaryReader(fs);//创建BinaryReader对象，用于写入下面的byte数组
    byte[] photo = br.ReadBytes((int)fs.Length); //新建byte数组，写入br中的数据
    br.Close();//记得要关闭br
    fs.Close();//还有fs
    string sql = "update Table1 set photo = @photo where ID = '0'";
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = "Data Source=.\\SQLExpress;Integrated Security=true;AttachDbFilename=|DataDirectory|\\Database.mdf;User Instance=true";
    SqlCommand cmd = new SqlCommand(sql, conn);
    SqlParameter sp = new SqlParameter("@photo", photo);
    cmd.Parameters.Add(sp);
    try
    {
        conn.Open();
        return (cmd.ExecuteNonQuery());
    }
    catch (Exception)
    {
        return -1;
        throw;
    }
    finally
    {
        conn.Close();
    }
}

public void ReadPhoto(string url)
    {
        string sql = "select photo from Table1 where ID = '0'";
        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = "Data Source=.\\SQLExpress;Integrated Security=true;AttachDbFilename=|DataDirectory|\\Database.mdf;User Instance=true";
        SqlCommand cmd = new SqlCommand(sql, conn);
        try
        {
            conn.Open();
            SqlDataReader reader = cmd.ExecuteReader();//采用SqlDataReader的方法来读取数据
            if (reader.Read())
            {
                byte[] photo = reader[0] as byte[];//将第0列的数据写入byte数组
                FileStream fs = new FileStream(url,FileMode.CreateNew);创建FileStream对象，用于写入字节数据流
                fs.Write(photo,0,photo.Length);//将byte数组中的数据写入fs
                fs.Close();//关闭fs
            }
            reader.Close();//关闭reader
        }
        catch (Exception ex)
        {
            throw;
        }
        finally
        {
            conn.Close();
        }
    }
}

　　

未采用SqlParameter，除了存在安全性问题，该方法还无法解决二进制流的更新，如图片文件。通过使用SqlParameter可以解决上述问题，常见的使用方法有两种，Add方法和AddRange方法。