Question

这是我在C＃中从sql数据库中检索图像的代码。我想将图像设置为图片框，但我得到“system.drawing.dll参数无效”

byte[] getImg;
     SqlConnection con2 = new SqlConnection(conString);
                con2.Open();
                if (con2.State == System.Data.ConnectionState.Open)
                {
                    string sss = "SELECT student_photo from student_reg where reg_year='" + year + "'and s_id='" +sid_lbl.Text+ "'";
                    SqlCommand cmd = new SqlCommand(sss, con2);
                    Console.WriteLine(sss);
                    SqlDataReader dr4 = cmd.ExecuteReader();

                    while (dr4.Read())
                    {



                        getImg = (byte[])(dr4["student_photo"]);






                    }
                    MemoryStream stream = new MemoryStream(getImg);
                    picturebox1.Image = Image.FromStream(stream);
    }
    con2.Close()

Answer 1

很难确定问题的位置，但尝试进行一些更改：

使用参数代替硬编码。在您的示例中，单引号暗示id和reg_year都是字符串。如果不是这种情况，则需要对参数值进行强数据类型化（转换为Int32或与数据库匹配的任何值）。你可以附上桌上的DDL吗？
如果您的输出是一行/一列，请考虑ExecuteScalar。

如果这不起作用，我的猜测是student_photo字段中不是真正的图像文件。

代码：

SqlConnection con2 = new SqlConnection(conString);
con2.Open();

if (con2.State == System.Data.ConnectionState.Open)
{
    string sss = "SELECT student_photo from student_reg where reg_year=@YEAR and s_id=@ID";
    SqlCommand cmd = new SqlCommand(sss, con2);
    cmd.Parameters.AddWithValue("@YEAR", year);
    cmd.Parameters.AddWithValue("@ID", sid_lbl.Text);

    Byte[] getImg = (Byte[])cmd.ExecuteScalar();
    MemoryStream stream = new MemoryStream(getImg);
    Image img = Image.FromStream(stream);

    picturebox1.Image = img;
}
con2.Close()

Answer 2

检查以下代码：

string stuImg  = string.Empty;       
         SqlConnection con2 = new SqlConnection(conString);
            con2.Open();
            if (con2.State == System.Data.ConnectionState.Open)
            {
                string sss = "SELECT student_photo from student_reg where  reg_year='" + year + "'and s_id='" +sid_lbl.Text+ "'";
                SqlCommand cmd = new SqlCommand(sss, con2);
                Console.WriteLine(sss);
                SqlDataReader dr4 = cmd.ExecuteReader();
                while (dr4.Read())
                {
                    stuImg =dr4["student_photo"].ToString();
                }
                var pic = Convert.FromBase64String(stuImg);
                using (MemoryStream ms = new MemoryStream(pic))
                  {
                   picturebox1.Image = Image.FromStream(ms);
                  }
              }

设置从sql数据库

2 个答案: