C# 当SQL BLOB不可用时，如何从.ashx加载默认映像

我是ASP&C的新手，一直不知道如何做到这一点

我通过

.ashx

文件从bd加载BLOB，就像so

一样，它工作正常，但有时没有BLOB或它是空的

这是基本代码

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["DataSource.iMIS.Connection"].ConnectionString);
        SqlCommand cmd = new SqlCommand("SELECT PICTURE_LOGO FROM Name_Picture WHERE ID = @EmpID", con);
        cmd.CommandType = CommandType.Text;
        cmd.Parameters.Add("@EmpID", id);

        con.Open();
        byte[] pict = (byte[])cmd.ExecuteScalar();
        con.Close();

        ctx.Response.ContentType = "image/bmp";
        ctx.Response.OutputStream.Write(pict, 0, pict.Length);

我的想法是在

con.Close（）

之后立即检查

pict.Length

，如果失败，我想显示默认图像，甚至文本

---

可能吗？怎么做？

经过更多的搜索和大量的“HttpCompileException（s）”，我终于找到了工作

感谢@Kazar在这里给出这个答案，感谢@Pranay Rana在这里给出这个答案

我把这些放在一起

        con.Open();
        byte[] pict = (byte[])cmd.ExecuteScalar();
        con.Close();

        ctx.Response.ContentType = "image/bmp";
        if (pict.Length <= 1) {
            // the BLOB is not a picture
            byte[] txt = ImageToByteArray(DrawText("no image found"));
            ctx.Response.OutputStream.Write(txt, 0, txt.Length);
        } else {
            // stream the picture data from BLOB
            ctx.Response.OutputStream.Write(pict, 0, pict.Length);
        }

con.Open（）；
字节[]pict=（字节[]）cmd.ExecuteScalar（）；
con.Close（）；
ctx.Response.ContentType=“image/bmp”；
如果（pict.Length经过更多的搜索和大量的“HttpCompileException（s）”，我就可以工作了

感谢@Kazar在这里给出这个答案，感谢@Pranay Rana在这里给出这个答案

我把这些放在一起

        con.Open();
        byte[] pict = (byte[])cmd.ExecuteScalar();
        con.Close();

        ctx.Response.ContentType = "image/bmp";
        if (pict.Length <= 1) {
            // the BLOB is not a picture
            byte[] txt = ImageToByteArray(DrawText("no image found"));
            ctx.Response.OutputStream.Write(txt, 0, txt.Length);
        } else {
            // stream the picture data from BLOB
            ctx.Response.OutputStream.Write(pict, 0, pict.Length);
        }

con.Open（）；
字节[]pict=（字节[]）cmd.ExecuteScalar（）；
con.Close（）；
ctx.Response.ContentType=“image/bmp”；
如果（pict.Length如果要在数据库中找不到映像时从磁盘加载映像，请使用此代码段

public void ProcessRequest(HttpContext context)
{
    //create a new byte array
    byte[] pict = new byte[0];

    //create a connection to the db and a command
    using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["DataSource.iMIS.Connection"].ConnectionString))
    using (SqlCommand command = new SqlCommand("SELECT PICTURE_LOGO FROM Name_Picture WHERE ID = @EmpID", connection))
    {
        //set the proper command type
        command.CommandType = CommandType.Text;

        //replace the parameters
        command.Parameters.Add("@EmpID", SqlDbType.Int).Value = id;

        try
        {
            //open the db and execute the sql string
            connection.Open();
            pict = (byte[])command.ExecuteScalar();
        }
        catch (Exception ex)
        {
            //catch any errors like unable to open db or errors in command. view with ex.Message
        }
    }

    //if no image found in database load the default from disk
    if (pict == null || pict.Length == 0)
    {
        pict = File.ReadAllBytes(context.Server.MapPath("/noimage.bmp"));
    }

    //clear the buffer stream
    context.Response.ClearHeaders();
    context.Response.Clear();
    context.Response.Buffer = true;

    //set the correct ContentType
    context.Response.ContentType = "image/bmp";

    //set the filename for the image
    context.Response.AddHeader("Content-Disposition", "attachment; filename=\"ImageName.bmp\"");

    //set the correct length of the string being send
    context.Response.AddHeader("content-Length", pict.Length.ToString());

    //send the byte array to the browser
    context.Response.OutputStream.Write(pict, 0, pict.Length);

    //cleanup
    context.Response.Flush();
    context.ApplicationInstance.CompleteRequest();
}

如果要在数据库中找不到映像时从磁盘加载映像，请使用此代码段

public void ProcessRequest(HttpContext context)
{
    //create a new byte array
    byte[] pict = new byte[0];

    //create a connection to the db and a command
    using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["DataSource.iMIS.Connection"].ConnectionString))
    using (SqlCommand command = new SqlCommand("SELECT PICTURE_LOGO FROM Name_Picture WHERE ID = @EmpID", connection))
    {
        //set the proper command type
        command.CommandType = CommandType.Text;

        //replace the parameters
        command.Parameters.Add("@EmpID", SqlDbType.Int).Value = id;

        try
        {
            //open the db and execute the sql string
            connection.Open();
            pict = (byte[])command.ExecuteScalar();
        }
        catch (Exception ex)
        {
            //catch any errors like unable to open db or errors in command. view with ex.Message
        }
    }

    //if no image found in database load the default from disk
    if (pict == null || pict.Length == 0)
    {
        pict = File.ReadAllBytes(context.Server.MapPath("/noimage.bmp"));
    }

    //clear the buffer stream
    context.Response.ClearHeaders();
    context.Response.Clear();
    context.Response.Buffer = true;

    //set the correct ContentType
    context.Response.ContentType = "image/bmp";

    //set the filename for the image
    context.Response.AddHeader("Content-Disposition", "attachment; filename=\"ImageName.bmp\"");

    //set the correct length of the string being send
    context.Response.AddHeader("content-Length", pict.Length.ToString());

    //send the byte array to the browser
    context.Response.OutputStream.Write(pict, 0, pict.Length);

    //cleanup
    context.Response.Flush();
    context.ApplicationInstance.CompleteRequest();
}

我是通过这篇文章来的，但我不明白我正在尝试实现这一点，但不知道如何“流”它我是通过这篇文章来的，但我不明白我正在尝试实现这一点，但不知道如何“流”它谢谢！这行代码
pict=File.ReadAllBytes（context.Server.MapPath（“/noimage.bmp”））；
正是我需要的。谢谢！这里的这一行
pict=File.ReadAllBytes（context.Server.MapPath（“/noimage.bmp”））
正是我所需要的。这种方法的好处是，您可以输出错误消息，或者动态更改文本/pic。这种方法的好处是，您可以动态输出错误消息，或者更改文本/pic。