VB.NET发送post请求的三种方式指定发送字符串内容、键值对和json串

 ''' 

    ''' 指定Post地址使用Get 方式获取全部字符串
    ''' 
    ''' 请求地址
    ''' 键值对
    ''' 返回字符串
    ''' 
    Public Function Post(ByVal url As String, ByVal dic As Dictionary(Of String, String)) As String
        Dim result As String = ""
        Dim req As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded;charset=UTF-8"
        Dim builder As StringBuilder = New StringBuilder()
        Dim i As Integer = 0
        For Each item In dic
            If i > 0 Then builder.Append("&")
            builder.AppendFormat("{0}={1}", item.Key, item.Value)
            i += 1
        Next
        Dim data As Byte() = Encoding.UTF8.GetBytes(builder.ToString())
        req.ContentLength = data.Length
        Using reqStream As Stream = req.GetRequestStream()
            reqStream.Write(data, 0, data.Length)
            reqStream.Close()
        End Using
        Dim resp As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
        Dim stream As Stream = resp.GetResponseStream()
        Using reader As StreamReader = New StreamReader(stream, Encoding.UTF8)
            result = reader.ReadToEnd()
        End Using

        Return result
    End Function

    ''' 

    ''' 指定Post地址使用Get 方式获取全部字符串
    ''' 
    ''' 请求地址
    ''' Post提交数据内容(utf-8编码的)
    ''' 返回字符串
    ''' 
    Public Function Post(ByVal url As String, ByVal content As String) As String
        Dim result As String = ""
        Dim req As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
        Dim data As Byte() = Encoding.UTF8.GetBytes(content)
        req.ContentLength = data.Length

        Using reqStream As Stream = req.GetRequestStream()
            reqStream.Write(data, 0, data.Length)
            reqStream.Close()
        End Using

        Dim resp As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
        Dim stream As Stream = resp.GetResponseStream()

        Using reader As StreamReader = New StreamReader(stream, Encoding.UTF8)
            result = reader.ReadToEnd()
        End Using

        Return result
    End Function

''' 

    ''' json串post请求
    ''' 
    ''' 
    ''' json字符串
    ''' 
    ''' 
    Public Function Post(ByVal url As String, ByVal postData As String) As String
        Dim result As String = ""
        Dim req As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
        req.Method = "POST"
        req.Timeout = "800"
        req.ContentType = "application/json"
        Dim data As Byte() = Encoding.UTF8.GetBytes(postData)
        req.ContentLength = data.Length

        Using reqStream As Stream = req.GetRequestStream()
            reqStream.Write(data, 0, data.Length)
            reqStream.Close()
        End Using

        Dim resp As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
        Dim stream As Stream = resp.GetResponseStream()

        Using reader As StreamReader = New StreamReader(stream, Encoding.UTF8)
            result = reader.ReadToEnd()
        End Using

        Return result
    End Function

json串最好新建一个实体类(tip:关键字和属性名冲突,可以中括号括起来声明[属性名]),实体类对象(new class.root)通过Newtonsoft.Json.dll序列化成json