如何在C＃中从数据库中恢复图像 [英] How Do I Retrive Image From Database In C#

问题描述

这里我使用来自db..kindly帮助的反向图像代码并纠正错误..

按钮点击事件：

here i use the code for retrive image from db..kindly help and rectify the error..
button click event:

SqlConnection c = new SqlConnection(@"Data Source=ADMIN-PC\SQLEXPRESS;Initial Catalog=Picture;Integrated Security=True");
          c.Open();

          MemoryStream stream = new MemoryStream();
          SqlCommand command = new SqlCommand("select * from pic where u='" + textBox1.Text + "'", c);
          byte[] image = (byte[])command.ExecuteScalar();
          stream.Write(image, 0, image.Length);
          c.Close();
          Bitmap bitmap = new Bitmap(stream);(Error thows here)
          pictureBox1.Image = bitmap;

显示错误：

It shows an error :

Argument exception was unhandled
parameter is not valid

推荐答案

请看这里：为什么我得到参数无效。我从数据库中读取图像时出现异常？ [ ^ ]

从一开始你的方法就错了。通过串联从UI获取的字符串组成的查询。不仅重复的字符串连接是低效的（因为字符串是不可变的;我是否必须解释为什么它会使重复连接变坏？），但是有更重要的问题：它打开了通向良好的大门已知的漏洞称为 SQL注入。



这是它的工作原理： http://xkcd.com/327 。



你明白了吗？从控件中获取的字符串可以是任何东西，包括......一段SQL代码。



怎么办？只需阅读有关此问题和主要补救措施：参数化语句： http://en.wikipedia.org/ wiki / SQL_injection 。



使用ADO.NET，使用：http://msdn.microsoft.com/en-us/library/ff648339.aspx 。



请参阅我过去的答案有更多细节：

在com.ExecuteNonQuery中更新EROR（ ）; ，

嗨名字没有显示在名称中？。

-SA

Your approach is wrong from the very beginning. The query composed by concatenation with strings taken from UI. Not only repeated string concatenation is inefficient (because strings are immutable; do I have to explain why it makes repeated concatenation bad?), but there is way more important issue: it opens the doors to a well-known exploit called SQL injection.

This is how it works: http://xkcd.com/327.

Are you getting the idea? The string taken from a control can be anything, including… a fragment of SQL code.

What to do? Just read about this problem and the main remedy: parametrized statements: http://en.wikipedia.org/wiki/SQL_injection.

With ADO.NET, use this: http://msdn.microsoft.com/en-us/library/ff648339.aspx.

Please see my past answers for some more detail:
EROR IN UPATE in com.ExecuteNonQuery();,
hi name is not displaying in name?.

—SA

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