我们上一篇文章讲了如果使用 net6 和 c# 来快速开发一个最简单的 teams meeting app。为了让大家比较容易理解，上个sample非常简单，简单到没有什么功能，那我们现在就来慢慢扩展这个app的功能：看看如何获取 meeting 的上下文。
打开上个sample中的 MainPage.cshtml 文件，使用如下代码：
@page "/MainPage"<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Demo</title><link rel="stylesheet" href="/static/styles.css"><script src="https://statics.teams.cdn.office.net/sdk/v1.10.0/js/MicrosoftTeams.min.js"integrity="sha384-6oUzHUqESdbT3hNPDDZUa/OunUj5SoxuMXNek1Dwe6AmChzqc6EJhjVrJ93DY/Bv"crossorigin="anonymous"></script>
</head>
<body><h1>MainPage</h1><div id="meeting-context"></h1><script>microsoftTeams.initialize();microsoftTeams.getContext(function(context) {document.getElementById('meeting-context').innerText = JSON.stringify(context);});</script>
</body>
</html>
这段代码比较简单，首先加入了对 teams js sdk 的引用，版本为 1.10.0，然后调用了下面这个方法：
microsoftTeams.initialize();
这个是对sdk的初始化，由于我们这个页面是会嵌入到 teams 会议中的，所以 MainPage 页面需要和 Teams客户端本身建立一种联系。这个是一个必要步骤，如果不做这个，其他大多数函数都会失败。
然后我们就调用了 microsoftTeams.getContext(function(context) { ... });，这就是用来获取会议上下文的 api。在sdk里，这个方法的定义如下。https://github.com/DefinitelyTyped/DefinitelyTyped/blob/8bd26b379caa1f82a24aa1bb768d92fe9f30950b/types/microsoftteams/index.d.ts
function getContext(callback: (context: Context) => void): void;interface Context {groupId?: string | undefined;teamId?: string | undefined;teamName?: string | undefined;channelId?: string | undefined;channelName?: string | undefined;channelType?: ChannelType | undefined;entityId: string;subEntityId?: string | undefined;locale: string;osLocaleInfo?: LocaleInfo | undefined;upn?: string | undefined;tid?: string | undefined;theme?: string | undefined;isFullScreen?: boolean | undefined;teamType?: TeamType | undefined;teamSiteUrl?: string | undefined;teamSiteDomain?: string | undefined;teamSitePath?: string | undefined;hostTeamTenantId?: string | undefined;hostTeamGroupId?: string | undefined;channelRelativeUrl?: string | undefined;sessionId?: string | undefined;userTeamRole?: UserTeamRole | undefined;chatId?: string | undefined;loginHint?: string | undefined;userPrincipalName?: string | undefined;userObjectId?: string | undefined;isTeamArchived?: boolean | undefined;hostClientType?: HostClientType | undefined;frameContext?: FrameContexts | undefined;sharepoint?: any;tenantSKU?: string | undefined;userLicenseType?: string | undefined;parentMessageId?: string | undefined;ringId?: string | undefined;appSessionId?: string | undefined;isCallingAllowed?: boolean | undefined;isPSTNCallingAllowed?: boolean | undefined;meetingId?: string | undefined;defaultOneNoteSectionId?: string | undefined;isMultiWindow?: boolean | undefined;appIconPosition?: number | undefined;sourceOrigin?: string | undefined;userClickTime?: number | undefined;teamTemplateId?: string | undefined;userFileOpenPreference?: FileOpenPreference | undefined;
}
可以看到 Context 是一个有非常多属性的结构，我们不展开，我们先来看一下安装后我们得到的 context是什么，在我们上面的代码里，我们把拿到的 context 序列化成 json，然后打印在页面上。
我们安装 app 到一个会议中，然后就可以看到页面上显示了 context 的json数据。
我们来看一下这个json里含了什么有用的信息：
{"locale": "en-us","theme": "default","entityId": null,"subEntityId": "","isFullScreen": false,"sessionId": "91291367-f8f0-9a5e-d420-490d4eb8bc8d","chatId": "19:meeting_ODA1MjIzYzAtODNhYy00MjE0LWFmZmQtN2MxMTQ0ODdlMWQ2@thread.v2","meetingId": "MCMxOTptZWV0aW5nX09EQTFNakl6WXpBdE9ETmhZeTAwTWpFMExXRm1abVF0TjJNeE1UUTBPRGRsTVdRMkB0aHJlYWQudjIjMA==","parentMessageId": "","hostClientType": "desktop","tenantSKU": "enterprise","jsonTabUrl": "microsoft-teams-json-tab.azurewebsites.net","userLicenseType": "Unknown","appSessionId": "1be21c3a-e846-4bf8-90e3-dc3b01938d39","appLaunchId": "d30e788c-d424-40f5-9373-236345d64249","isMultiWindow": false,"appIconPosition": 23,"userClickTime": 1640572621827,"sourceOrigin": null,"userFileOpenPreference": "inline","osLocaleInfo": {"platform": "windows","regionalFormat": "en-us","longDate": "dddd, MMMM d, yyyy","shortDate": "M/d/yyyy","longTime": "h:mm:ss tt","shortTime": "h:mm tt"},"frameContext": "content","teamSiteDomain": "aabbcc365.sharepoint.com","teamSitePath": "","teamSiteUrl": "","ringId": "general","tid": "53213f63-c1e6-4416-bdab-da54fcb7b4b7","loginHint": "admin@aabbcc365.onmicrosoft.com","upn": "admin@aabbcc365.onmicrosoft.com","userPrincipalName": "admin@aabbcc365.onmicrosoft.com","userObjectId": "488e5982-c57c-4373-a4dd-67eab506d98d"
}
有这么一些信息我觉得比较有用：
- locale 当前 Teams 客户端的语言
- theme 当前 Teams 客户端的主题，比如是不是暗色主题，或者是高对比度主题
- meetingId 当前会议的唯一id
- hostClientType 当前 Teams 客户端的类型
enum HostClientType {desktop = "desktop",web = "web",android = "android",ios = "ios",rigel = "rigel",surfaceHub = "surfaceHub" } - osLocaleInfo 当前 Teams 客户端的文化信息，比如日期格式之类的
- tid 当前租户的id
- userPrincipalName 用户名
- userObjectId 当前用户的 Azure AD里的Object ID
我们有了这些信息后（特别是meeting id），后面很多 api 就比较容易调用了，我们将在后面的文章里再具体展开。
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