Question

我有一个名为Functions的类，它将存储Insert，Update和Delete函数。问题是我无法弄清楚如何传递图像（我从图片框中获取）。这是我尝试过的：函数类：

 public static Functions Insert(String u, String v, byte[] img)
        {

 String query = string.Format("INSERT INTO example(Name, Description) VALUES ('{0}', '{1}, {2}')", u, v,img);
            MySqlCommand cmd = new MySqlCommand(query, dbConn);

            dbConn.Open();

            cmd.ExecuteNonQuery();

            if (cmd.ExecuteNonQuery() == 1)
            {
                MessageBox.Show("Succesfully added!");

            }

            int id = (int)cmd.LastInsertedId;

            Functions func = new Functions(id,u,v,img);

            dbConn.Close();

            return func;

        }

Form1中的按钮：

    private void button2_Click(object sender, EventArgs e)
    {

        String u = textBox2.Text;
        String v = textBox3.Text;


        MemoryStream ms = new MemoryStream();
        pictureBox1.Image.Save(ms, pictureBox1.Image.RawFormat);
        byte[] img = ms.ToArray();


        currf = Functions.Insert(u, v, img);
    }

以下是错误消息：

未处理的类型＆＃39; MySql.Data.MySqlClient.MySqlException＆＃39;   发生在MySql.Data.dll
中
其他信息：字段＆＃39;图像＆＃39;没有默认值

Answer 1

在查询中使用参数非常简单。首先，使用占位符为参数准备sql命令文本。然后将参数添加到MySqlCommand.Parameters集合中，最后将所有内容传递给使用参数集合的数据库引擎，以便将数据正确地插入到基础表中

// Notice that you are missing the third field (the image one)
// Please replace Image with the correct name of the image field in your table
string query = @"INSERT INTO example (Name, Description, Image) 
                 VALUES (@name, @description, @img";
MySqlCommand cmd = new MySqlCommand(query, dbConn);
cmd.Parameters.Add("@name", MySqlDbType.VarChar).Value = u;
cmd.Parameters.Add("@description", MySqlDbType.VarChar).Value = v;
cmd.Parameters.Add("@img", MySqlDbType.Binary).Value = img;
dbConn.Open();
// Do not execute the query two times.
// cmd.ExecuteNonQuery();
if (cmd.ExecuteNonQuery() == 1)
{
    MessageBox.Show("Succesfully added!");
    int id = (int)cmd.LastInsertedId;
    ....
}
else
{
    // failure msg ?
}

C＃MySql连接。如何传递图像？

1 个答案: