Question

对于学校项目，我必须建立一个网上商店。我试图从数据库中获取产品图像，但我似乎无法使其工作我在互联网上的某处读到你应该通过一个处理程序来做到这一点就是这样：

public class afbeelding : IHttpHandler
{

    public void ProcessRequest(HttpContext context)
    {
        //Connect
        string connectionstring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\jeroen\Documents\Visual Studio 2010\Projects\producten\producten\App_Data\Bimsports.accdb;Persist Security Info=True";
        OleDbConnection conn = new OleDbConnection(connectionstring);

        //execute
        int artikelnummer = 1;
        string sql = "SELECT foto FROM Artikel WHERE Artikelnummer =?";
        OleDbCommand cmd = new OleDbCommand(sql, conn);
        cmd.Parameters.AddWithValue("Artikelnummer", artikelnummer);
        //read
        try
        {
            conn.Open();
            OleDbDataReader reader = cmd.ExecuteReader();
            reader.Read();
            context.Response.BinaryWrite((byte[])reader["foto"]);
        }

        catch 
        {

        }
        finally
        {
            conn.Close();
        }

我应该把它放在aspx中：

<asp:Image ID="img_nikeshirt" runat="server" ImageUrl='<%# "afbeelding.ashx?ID=" + Eval("artikelnummer")%>'/>

我没有错误，但图片不会显示。有人可以帮我吗？

编辑：

顺便提一下，图像在访问数据库中。它说ole对象。它仍然被认为是一个形象？

另一个编辑：

如果我直接将查询放入访问权限，它会给我图片的列而不是图片本身......这可能是问题吗？如果是这样我该如何解决？

Answer 1

您应该在响应中设置Content-Type标头，如下所示：

context.Response.ContentType = "image/png";
context.Response.BinaryWrite((byte[])reader["foto"]);
context.Response.Flush();

Answer 2

您是否尝试返回该HTTP响应消息？

而不是void返回byte []

的上下文

Answer 3

我知道这里的人们发现我错过了很多代码，而且出于某种原因，通过访问本身保存图像并不起作用。我做了一个页面，在那里加载它。对于有同样问题的人来说，这是我的代码。

用于将图像保存在数据库中的webform

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>

</div>
<asp:DropDownList ID="ddlartikel" runat="server" AutoPostBack="true" 
    onselectedindexchanged="ddlartikel_SelectedIndexChanged">
</asp:DropDownList>
<br />
<asp:Image ID="imgfoto" runat="server" />
<p>Verander Foto's</p>
<asp:FileUpload ID="FileUpload1" runat="server" />
<br />
<asp:Button ID="btnsave" runat="server" Text="Sla op in database" 
    onclick="btnsave_Click" />
</form>
</body>
</html>

用于将图像保存到数据库的webform背后的代码

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {

                //Connect
                string connectionstring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\jeroen\Documents\Visual Studio 2010\Projects\producten\producten\App_Data\Bimsports.accdb;Persist Security Info=True";
                OleDbConnection conn = new OleDbConnection(connectionstring);


                //Execute
                string sql = "SELECT Artikelnummer, Omschrijving FROM Artikel";
                OleDbCommand cmd = new OleDbCommand(sql, conn);
                //Read
                try
                {
                    conn.Open();
                    OleDbDataReader reader = cmd.ExecuteReader();
                    ddlartikel.DataSource = reader;
                    ddlartikel.DataValueField = "artikelnummer";
                    ddlartikel.DataTextField = "omschrijving";
                    ddlartikel.DataBind();
                }
                    finally{conn.Close();}
                FetchPicture();
            }
        }

        protected void ddlartikel_SelectedIndexChanged(object sender, EventArgs e)
        {
            FetchPicture();
        }
        private void FetchPicture()
        {
            if (ddlartikel.SelectedIndex > -1)
            {
                int artikelnummer = Convert.ToInt32(ddlartikel.SelectedValue);
                string sUrl = string.Format("~/afbeelding.ashx?artikelnummer={0}", artikelnummer);
                imgfoto.ImageUrl = sUrl;
            }
        }

        protected void btnsave_Click(object sender, EventArgs e)
        {
            if (FileUpload1.HasFile)
            {
                byte[] MyData = FileUpload1.FileBytes;

                int artikelnummer = Convert.ToInt32(ddlartikel.SelectedValue);
                CBlob.SavePicture(artikelnummer, MyData);
            }
        }


    }
}

用于从数据库（您的网页）检索图像的网络表单

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

        Merk:
        <asp:Label ID="lbl_merk" runat="server"></asp:Label>
        <br />
        Maat:
        <asp:Label ID="lbl_maat" runat="server"></asp:Label>
        <br />
        Omschrijving:
        <asp:Label ID="lbl_omschrijving" runat="server"></asp:Label>
        <br />
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
        Kleur:
        <asp:Label ID="lbl_kleur" runat="server"></asp:Label>
        <br />
        Prijs:
        <asp:Label ID="lbl_prijs" runat="server"></asp:Label>
        <br />
        BTW:
        <asp:Label ID="lbl_btw" runat="server"></asp:Label>
        <br />
        Categorie: 
        <asp:Label ID="lbl_categorie" runat="server"></asp:Label>

        <br />

        <br />
        <asp:Image ID="img_nikeshirt" runat="server" ImageUrl='<%# "afbeelding.ashx?ID=" + Eval("artikelnummer")%>'/>    
    </div>

    </form>
</body>
</html>

网页背后的代码

protected void Page_Load（object sender，EventArgs e） { int artikelnummer = 1; //连接 string connectionstring = @＆＃34; Provider = Microsoft.ACE.OLEDB.12.0; Data Source = C：\ Users \ jeroen \ Documents \ Visual Studio 2010 \ Projects \ producten \ producten \ App_Data \ Bimsports.accdb; Persist Security Info =真＆＃34 ;; OleDbConnection conn = new OleDbConnection（connectionstring）;

    //Execute
    string sql = "SELECT Merk, Maat, Omschrijving, Kleur, Prijs, BTW, Categorie.Categorie FROM Artikel INNER JOIN Categorie ON Artikel.Categorie = Categorie.Categorienummer WHERE Artikelnummer =?";
    OleDbCommand cmd = new OleDbCommand(sql, conn);
    cmd.Parameters.AddWithValue("Artikelnummer", artikelnummer);
    //Read
    try
    {
        conn.Open();
        OleDbDataReader reader = cmd.ExecuteReader();

        while (reader.Read())
        {
            lbl_merk.Text = reader["Merk"].ToString();
            lbl_maat.Text = reader["Maat"].ToString();
            lbl_omschrijving.Text = reader["Omschrijving"].ToString();
            lbl_kleur.Text = reader["Kleur"].ToString();
            lbl_prijs.Text = reader["Prijs"].ToString();
            lbl_btw.Text = reader["BTW"].ToString();
            lbl_categorie.Text = reader["Categorie"].ToString();
        }
        string sUrl = string.Format("~/afbeelding.ashx?artikelnummer={0}", artikelnummer);
        img_nikeshirt.ImageUrl = sUrl;

    }
    catch
    {

    }
    finally
    {
        conn.Close();
    }
}

然后我创建了一个类，它查看您请求的数据库中的图像，并将其放在byte []

中

       public static byte[] getpicture(int artikelnummer)
        {
            string connectionstring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\jeroen\Documents\Visual Studio 2010\Projects\producten\producten\App_Data\Bimsports.accdb;Persist Security Info=True";
            OleDbConnection conn = new OleDbConnection(connectionstring);
            //Execute
            string sql = "SELECT foto FROM Artikel WHERE Artikelnummer =?";
            OleDbCommand cmd = new OleDbCommand(sql, conn);
            cmd.Parameters.AddWithValue("Artikelnummer", artikelnummer);
            try
            {
                byte[] photodata = null;
                conn.Open();
                OleDbDataReader reader = cmd.ExecuteReader();

                if (reader.HasRows)
                {
                    reader.Read();
                    if (!reader.IsDBNull(0))
                    {
                        photodata = new byte[Convert.ToInt32((reader.GetBytes(0, 0, null, 0, Int32.MaxValue)))];
                        long bytesreceived = reader.GetBytes(0, 0, photodata, 0, photodata.Length);
                    }
                }
                return photodata;
            }
            catch (Exception ex)
            {
            }
            finally
            {
                conn.Close();
            }
            return null;
        }
        public static bool SavePicture(int artikelnummer, byte[] photodata)
        {
            int rowupdated = 0;

            string connectionstring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\jeroen\Documents\Visual Studio 2010\Projects\producten\producten\App_Data\Bimsports.accdb;Persist Security Info=True";
            OleDbConnection conn = new OleDbConnection(connectionstring);

            string sql = "UPDATE Artikel SET foto=? WHERE artikelnummer=?";
            OleDbCommand cmd = new OleDbCommand(sql, conn);


            conn.Open();

            OleDbParameter param = new OleDbParameter("@foto", OleDbType.VarBinary, photodata.Length);
            param.Value = photodata;
            cmd.Parameters.Add(param);
            cmd.Parameters.AddWithValue("Artikelnummer", artikelnummer);
            rowupdated = (int)cmd.ExecuteNonQuery();

            return (rowupdated>0);



        }
    }
}

并且处理程序正在页面上写它。

public class afbeelding : IHttpHandler
{

    public void ProcessRequest(HttpContext context)
    {
        int artikelnummer = 0;

        if (context.Request.QueryString["artikelnummer"] != null)
        {
            artikelnummer = int.Parse(context.Request.QueryString["artikelnummer"]);
        }
        if (artikelnummer != 0)
        {
            byte[] bytes = CBlob.getpicture(artikelnummer);

            if (bytes != null)
            {
                context.Response.ContentType = "image/jpeg";
                context.Response.OutputStream.Write(bytes, 0, bytes.Length);
            }
        }
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

它可能更容易和更短，但嘿，它的工作原理！感谢所有输入

关于tuinj

使用处理程序从数据库中检索图像

3 个答案: