显示图像（来自数据库）基于雇员的图像控制的图像控制

Question

Triyng来检索和显示图像从数据库... 我已在其中我有此一个HttpHandler：

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest 

    'context.Response.ContentType = "text/plain" 
    'context.Response.Write("Hello World!") 

    Dim employeeId As Integer 
    If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then 
     employeeId = Convert.ToInt32(context.Request.QueryString("employeeId")) 
    Else 
     Throw New ArgumentException("No parameter specified") 
    End If 
    Dim imageData() As Byte = {} 
    ' get the image data from the database using the employeeId Querystring 
    context.Response.ContentType = "image/jpeg" 
    ' You can retrieve this also from the database 
    context.Response.BinaryWrite(imageData) 

End Sub 

Protected Sub DisplayButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles DisplayButton.Click 
    bind() 
    GridView1.Visible = "True" 
    ProcessRequest(Context) 
End Sub 

错误：The 'MasterPageFile' property can only be set in or before the 'Page_PreInit' event. 我哪里错了？我需要做什么改变？

这是窗体上的图像控制：

<asp:Image ID="Image1" runat="server" imageUrl="HttpHandler.ashx?employeeId=5"/> 

@Stefano阿尔铁：

这是Employee.aspx

Protected Sub DisplayButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles DisplayButton.Click 
    bind() 
    GridView1.Visible = "True" 
    Image1.ImageUrl = "~/HttpHandler.ashx?EmployeeID='" & EmailIDTextBox.Text & "'" 
End Sub 

，这是上HttpHandler.ashx

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest 

    'context.Response.ContentType = "text/plain" 
    'context.Response.Write("Hello World!") 

    Dim employeeId As Integer 
    If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then 
     employeeId = Convert.ToInt32(context.Request.QueryString("employeeId")) 
    Else 
     Throw New ArgumentException("No parameter specified") 
    End If 
    Dim imageData() As Byte = {} 
    ' get the image data from the database using the employeeId Querystring 
    context.Response.ContentType = "image/jpeg" 
    ' You can retrieve this also from the database 
    context.Response.BinaryWrite(imageData) 

End Sub 

Answer 1

通用H andler五月帮助你..

Answer 2

处理程序应该是这样的

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest 
Dim employeeId As Integer 
If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then 
employeeId = Convert.ToInt32(context.Request.QueryString("employeeId")) 
Dim con As SqlConnection("your connection string")  
Dim cmd As SqlCommand("select image_colum from <table_name> where employeeID = "+employeeID) 
con.Open() 
Dim dr As SqlDataReader = cmd.ExecuteReader() 
dr.Read() 
Dim picture As Byte() = dr[0] 
context.Response.ContentType = "image/jpeg" 
context.Response.BinaryWrite(picture) 
End If 
End Sub