說起來，查看Mongodb官方的接口文檔是場噩夢，盡管mongodb官方花了大力氣整頓了它的API，但是簡單的接口羅列，0代碼示范，讓人無從開始。幸虧有很多天才，成功破譯，我才得以沿著他們走的路，照貓畫虎的走下去。整個項目結構如下：
類文件中vbtest.vb數據庫實體類對應著mongodb文檔vbtest，用于數據操作測試
Imports MongoDB.BsonPublic Class vbtest Public _id As ObjectId Public content As StringEnd Class
（optional）vbmongo.vb是綁定好數據庫實體類vbtest的版本
Imports MongoDB.BsonImports MongoDB.DriverPublic Class vbmongo Public client Public collection As IMongoCollection(Of vbtest) Public database As IMongoDatabase Public mlist As List(Of vbtest) Public builder As FilterDefinitionBuilder(Of vbtest) = New FilterDefinitionBuilder(Of vbtest) Public filter As FilterDefinition(Of vbtest) Public Sub New(ByVal dbname As String, ByVal collectionname As String) client = New MongoClient("mongodb://127.0.0.1:27017") database = client.GetDatabase(dbname) collection = database.GetCollection(Of vbtest)(collectionname) End Sub Public Async Function loadrecords() As Task(Of List(Of vbtest)) filter = builder.Ne(Of ObjectId)("_id", New ObjectId())//_id不等于空的記錄，通過這種方法蹩腳的實現了查找全部的功能Builder的大多數條件設置函數都用到了泛型Ne（Of TField） Dim mlist As List(Of vbtest) = Await collection.Find(filter).ToListAsync()//TField可以理解為 type of field 對應的是實體類中字段的數據類型例如 OBjectId或者String等等 Return mlist End Function Public Async Function loadone(ByVal _id As String) As Task(Of vbtest) filter = builder.Eq(Of ObjectId)("_id", New ObjectId(_id)) Dim mlist As vbtest = Await collection.Find(filter).FirstOrDefaultAsync() Return mlist End Function Public Async Function updateone(ByVal _id As String, ByVal doc As vbtest) As Task(Of vbtest) filter = builder.Eq(Of ObjectId)("_id", New ObjectId(_id)) Dim up As UpdateDefinitionBuilder(Of vbtest) = New UpdateDefinitionBuilder(Of vbtest)() Dim updef As UpdateDefinition(Of vbtest) updef = up.Set(Of String)("content", doc.content) '.Set(Of String)("content", doc) collection.UpdateOneAsync(filter, updef) End FunctionEnd Class說起來mongodb的連接可以分幾步，根據連接字符串打開鏈接，獲取數據庫，獲取文檔，進而在文檔的基礎上進行增刪改查。對于vb.net操作mongodb，完全是根據c#的操作范例，根據vb.net的語法特點臨摹出來的。
首先需要對項目進行Nuget包的安裝，我們要搜尋的是MongoDB.Driver
這里創建了一個vb.net的泛型類vbmongoT，只寫了單個查找，查找列表和更新操作，函數中大量成對出現了Async和Await關鍵字，用于標識該功能使用了異步編程,在窗體程序中進行調用的時候，仍需要在成對的使用Async Await的關鍵字，因為異步函數返回的往往是Task<TResult>類型（c#）或者 Task（Of TResult） （vb.net）需要在調用函數體中使用await關鍵字拿到最終結果Imports MongoDB.BsonImports MongoDB.Driver
Public Class vbmongoT(Of T) Public client Public collection As IMongoCollection(Of T) Public database As IMongoDatabase Public mlist As List(Of T) Public builder As FilterDefinitionBuilder(Of T) = New FilterDefinitionBuilder(Of T) Public up As UpdateDefinitionBuilder(Of T) Public updef As UpdateDefinition(Of T) Public filter As FilterDefinition(Of T) Public Sub New(ByVal dbname As String, ByVal collectionname As String) client = New MongoClient("mongodb://127.0.0.1:27017") database = client.GetDatabase(dbname) collection = database.GetCollection(Of T)(collectionname) End Sub Public Async Function loadrecords() As Task(Of List(Of T)) filter = builder.Ne(Of ObjectId)("_id", New ObjectId()) Dim mlist As List(Of T) = Await collection.Find(filter).ToListAsync() Return mlist End Function Public Async Function loadone(ByVal _id As String) As Task(Of T) filter = builder.Eq(Of ObjectId)("_id", New ObjectId(_id))//_id滿足查找條件的記錄，Builder的大多數條件設置函數都用到了泛型：例如Ne（Of TField） Dim mlist As T = Await collection.Find(filter).FirstOrDefaultAsync() Return mlist End Function Public Async Function updateone(ByVal filter As FilterDefinition(Of T), ByVal updef As UpdateDefinition(Of T)) As Task(Of T) 'updef = up.Set(Of String)("content", doc.content) '.Set(Of String)("content", doc) Await collection.UpdateOneAsync(filter, updef) End Function End Class在mongodb這一版本的官方API里，IMongoCollection對象是查找，添加，更新，刪除等動作的發起者，這里面查找，更新，刪除都要用到查詢條件，
官方謂之filter（過濾器）C#: FilterDefinition<T> VB.net:FilterDefinition (Of T)
而過濾器是過濾器模具的建模結果
過濾器模具：C#: FilterDefinitionBuilder<T> VB.net:FilterDefinitionBuilder (Of T)
在Mongodb.Driver這個大類下面 建議直接翻看FilterDefinitionBuilder的介紹 https://mongodb.github.io/mongo-csharp-driver/2.10/apidocs/html/T_MongoDB_Driver_FilterDefinitionBuilder_1.htm
同樣的數據庫文檔的更新操作由UpdateDefinitionBuilder 設置更新字段后產生的 UpdateDefinition完成
窗體程序部分
Imports MongoDB.BsonImports MongoDB.DriverPublic Class Form1 Public client Public bsdoc As vbtest Public collection As IMongoCollection(Of vbtest) Public database As IMongoDatabase Public mlist As List(Of vbtest) Public builder As FilterDefinitionBuilder(Of vbtest) = New FilterDefinitionBuilder(Of vbtest) Public vm As vbmongoT(Of vbtest) = New vbmongoT(Of vbtest)("meandmycoach", "vbtest") Public filter As FilterDefinition(Of vbtest) Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click bsdoc.content = RichTextBox1.Text vm.filter = vm.builder.Eq(Of ObjectId)("_id", New ObjectId(ComboBox1.Text)) vm.up = New UpdateDefinitionBuilder(Of vbtest) vm.updef = vm.up.Set(Of String)("content", bsdoc.content) 'vm.up.Set(Of String)("content", bsdoc.content) vm.updef = vm.up.Combine(vm.updef) vm.updateone(vm.filter, vm.updef) End Sub Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load vm = New vbmongoT(Of vbtest)("meandmycoach", "vbtest") Dim bsdoc As vbtest = New vbtest() End Sub Private Async Sub PictureBox1_Click(sender As Object, e As EventArgs) Handles PictureBox1.Click mlist = Await vm.loadrecords() For i As Integer = 0 To mlist.Count - 1 ComboBox1.Items.Add(mlist(i)._id.ToString()) Next ComboBox1.Text = ComboBox1.Items(0) Label2.Text = mlist.Count.ToString() End Sub Private Sub RichTextBox1_TextChanged(sender As Object, e As EventArgs) Handles RichTextBox1.TextChanged End Sub Private Async Sub ComboBox1_TextChanged(sender As Object, e As EventArgs) Handles ComboBox1.TextChanged bsdoc = Await vm.loadone(ComboBox1.Text) RichTextBox1.Text = bsdoc.content End Sub Private Async Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged End SubEnd Class功能描述：通過點擊圖片，加載所有的vbtest文檔記錄，combobox1專門用于顯示ObjectId，可以通過ToString()方法轉換為普通字符串
隨著下拉框ObjectId的改變，richtext1控件加載vbtest實體類對應記錄的Content字段，可以更改字段內容后點擊更新提交按鈕完成文檔的UpdateOneAsync操作
總結
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