ajax - 使用 VB.NET、AJAX 和 NPGSQL 连接到 PostgreSQL

Question

我正在尝试在 VB.NET 和/或 .asp 中编写一个脚本，该脚本将使用 NPGSQL 数据提供程序连接到我的 PostgreSQL 数据库。

此函数使用 AJAX 获取值 (selectedFT) 并将该值发送到 helloWorld.asp 脚本。这部分工作正常。

function ajaxyThing (selectedFT) {

var xmlhttp; //CREATE THE VARIABLE TO HOLD THE XMLHTTPRequest OBJEcT
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari THESE BROWSERS SUPPORT THE   XMLHTTPRequest OBJECT
  xmlhttp=new XMLHttpRequest();  //CREATE THE XMLHTTPRequest OBJECT
  }
else
 {// code for IE6, IE5 THESE BROWSERS DO NOT SUPPORT THE XMLHTTPRequest OBJECT AND NEED    AND ACTIVEXOBJECT
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); //CREATE THE ActiveXObject
  }
//When using Async = true specify a function to execute when the reponse is ready in     the onreadystatechange event
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
    document.getElementById("responseText").innerHTML = xmlhttp.responseText;
}
}

//TO SEND A REQUEST TO A SERVER, WE USE THE open() AND send() METHODS OF THE     XMLHttpRequest object
xmlhttp.open("GET", "helloWorld.asp?q="+ selectedFT, true);
xmlhttp.send();
}

接下来我需要 ASP 脚本(或 .aspx 或 .ashx。我不知道什么是最好的方法)来使用 selectedFT 值来查询我的 PostgreSQL 数据库。这是我遇到麻烦的地方。我知道我需要做以下事情，但我不知道如何将它们放在一起:

1) 从 AJAX http 请求中获取值。例如我应该使用:

response.expires=-1
q= request.querystring("q")

2) 然后我需要建立到 PostgreSQL 数据库的连接。我使用以下代码(取自本网站 http://www.techrepublic.com/article/easily-integrate-postgresql-with-net/6102826)在标准 .aspx 页面的 PageLoad 中运行，它可以很好地将数据绑定(bind)到 gridview。但我真正需要的不是将结果集连接到 gridview，而是让我的连接脚本独立，这样我就可以使用输出来做很多不同的事情。我不确定如何在 .asp 脚本(或 .aspx 或 .ashx)中实现此代码，并在我从 AJAX 函数调用 .asp 脚本(或 .aspx 或 .ashx)时使其运行。

 Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)Handles MyBase.Load

    Dim pgConnection As NpgsqlConnection = New NpgsqlConnection
    Dim pgCommand As NpgsqlCommand = New NpgsqlCommand
    Dim pgConnectionString As String
    Dim sda As NpgsqlDataAdapter

    Dim ds As DataSet
    ds = New DataSet

    pgConnectionString = "Server=localhost;Port=5432;Userid=myUserId;Database=myDatabaseName;password=myPassword;Protocol=3;SSL=false;Pooling=true;MinPoolSize=1;MaxPoolSize=20;Encoding=UNICODE;Timeout=15;SslMode=Disable"
    pgConnection.ConnectionString = pgConnectionString
    pgConnection.Open()
    pgCommand.Connection = pgConnection
    pgCommand.CommandType = CommandType.Text

    pgCommand.CommandText = "SELECT * FROM ""myTable"";"

    If pgConnection.FullState = ConnectionState.Open Then
        MsgBox("Connection To PostGres is open", MsgBoxStyle.MsgBoxSetForeground)
    End If

    sda = New NpgsqlDataAdapter(pgCommand)
    sda.Fill(ds)
    GridView1.DataSource = ds
    GridView1.DataBind()

    pgConnection.Close()
End sub

如有任何建议，我们将不胜感激。谢谢!

Answer 1

经过一番挖掘，我找到了解决这个问题的方法。这是我使用 NPGSQL 数据连接器、ASP.NET (VB.NET)、Javascript 和 AJAX 从 PostGresql 数据库查询的解决方案。在我的应用程序中，名为“ajaxThing”的 AJAX 函数从 OpenLayers map 中的自定义控件接收值，但您可以将任何值传递给该函数。

这是我的 javascript 文件中 Ajax 函数的代码:

function ajaxyThing (selectedFT) {
var xmlhttp; //CREATE THE VARIABLE TO HOLD THE XMLHTTPRequest OBJEcT
if (window.XMLHttpRequest)
 {// code for IE7+, Firefox, Chrome, Opera, Safari THESE BROWSERS SUPPORT THE     XMLHTTPRequest OBJECT
  xmlhttp=new XMLHttpRequest();  //CREATE THE XMLHTTPRequest OBJECT
  }
else
  {// code for IE6, IE5 THESE BROWSERS DO NOT SUPPORT THE XMLHTTPRequest OBJECT AND NEED AND ACTIVEXOBJECT
 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); //CREATE THE ActiveXObject
}
//When using Async = true specify a function to execute when the reponse is ready in the onradystatechange event
xmlhttp.onreadystatechange = function () {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        document.getElementById("divAttributes").innerHTML = xmlhttp.responseText;
    }
}

//TO SEND A REQUEST TO A SERVER, WE USE THE open() AND send() METHODS OF THE     XMLHttpRequest object
xmlhttp.open("GET", "Handler.ashx?q="+ selectedFT, true);
xmlhttp.send();
}

然后在 Microsoft Visual Web Developer Express 2010 中，我创建了一个 Web 处理程序 (.ashx) 文件，并将变量从我的 AJAX 函数传递给它。我将变量“selectedFT”传递给 Visual Studio Web 处理程序。以下是网络处理程序的代码:

<%@ WebHandler Language="VB" Class="Handler" %>

Imports System
Imports System.Web
Imports Npgsql
Imports System.Data   

Public Class Handler : Implements IHttpHandler

    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
    context.Response.Expires = -1
    Dim q = context.Request.QueryString("q") 

    Dim pgConnection As NpgsqlConnection = New NpgsqlConnection
    Dim pgCommand As NpgsqlCommand = New NpgsqlCommand
    Dim pgConnectionString As String
    Dim sda As NpgsqlDataAdapter

    Dim ds As DataSet
    ds = New DataSet

    pgConnectionString = "Server=localhost;Port=5432;Userid=myPostGresUserId;Database=myDatabaseName;password=myPassword;Protocol=3;SSL=false;Pooling=true;MinPoolSize=1;MaxPoolSize=20;Encoding=UNICODE;Timeout=15;SslMode=Disable"
    pgConnection.ConnectionString = pgConnectionString
    pgConnection.Open()
    pgCommand.Connection = pgConnection
    pgCommand.CommandType = CommandType.Text

    pgCommand.CommandText = "SELECT * FROM ""myTable"" WHERE ""myValue"" = '" & q & "';"

    sda = New NpgsqlDataAdapter(pgCommand)
    sda.Fill(ds)

    If pgConnection.FullState = ConnectionState.Open Then
        context.Response.Write("<table>")
        Dim dr As DataRow
        Dim dt As DataTable
        dt = ds.Tables(0)
        For Each dr In dt.Rows
            context.Response.Write("<tr><td><b>Column #1 Name:</b></td><td>" & dr.Item(0) & "</td></tr>") 
            context.Response.Write("<tr><td><b>Column #2 Name:</b></td><td>" & dr.Item(1) & "</td></tr>") 
            context.Response.Write("<tr><td><b>Column #3 Name:</b></td><td>" & dr.Item(2) & "</td></tr>") 
            Next
        ds.Dispose()
        context.Response.Write("</table>")
    Else
        context.Response.Write("pgConnection did not open successfully.")
    End If

    pgConnection.Close()

End Sub

Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
    Get
        Return False
    End Get
End Property

End Class

我不会声称这是解决问题的最佳方案 - 但它确实有效。我愿意接受您可能提出的任何建议，以使其更加优雅。谢谢!