如何在带O365认证的WebForms站点获取登录用户邮箱并实现个性化展示？

Hey there! Since you've already got your O365 authentication up and running via Visual Studio's built-in setup, grabbing the logged-in user's email and customizing content based on that is straightforward. Let's walk through how to do this:

When using O365 authentication in WebForms, the user's identity data is stored in a ClaimsPrincipal object. The email address is typically available as a claim—you can retrieve it in your page's code-behind (.aspx.cs) like this:

using System.Security.Claims;
using System;

protected void Page_Load(object sender, EventArgs e)
{
    if (User.Identity.IsAuthenticated)
    {
        // First try the standard Email claim type
        var emailClaim = ((ClaimsPrincipal)User).FindFirst(ClaimTypes.Email);
        string userEmail = null;

        if (emailClaim != null)
        {
            userEmail = emailClaim.Value;
        }
        // Fallback to "preferred_username" (O365 sometimes uses this for emails)
        else
        {
            var preferredNameClaim = ((ClaimsPrincipal)User).FindFirst("preferred_username");
            if (preferredNameClaim != null)
            {
                userEmail = preferredNameClaim.Value;
            }
        }

        if (!string.IsNullOrEmpty(userEmail))
        {
            // Store the email for later use (e.g., in ViewState) or display it
            ViewState["UserEmail"] = userEmail;
            lblUserEmail.Text = $"Logged in as: {userEmail}";
        }
    }
}

Once you have the user's email, you can customize content in two main ways:

1. 后端代码控制（Code-Behind） #

Use server-side logic to show/hide controls or redirect users based on their email:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack && User.Identity.IsAuthenticated)
    {
        var emailClaim = ((ClaimsPrincipal)User).FindFirst(ClaimTypes.Email);
        if (emailClaim != null)
        {
            string userEmail = emailClaim.Value;

            // Show admin-only link for specific email
            if (userEmail.Equals("admin@yourdomain.com", StringComparison.OrdinalIgnoreCase))
            {
                lnkAdminPanel.Visible = true;
                lnkUserDashboard.Visible = false;
            }
            else
            {
                lnkAdminPanel.Visible = false;
                lnkUserDashboard.Visible = true;
            }

            // Redirect VIP users to their exclusive page
            if (userEmail.Equals("vip@yourdomain.com", StringComparison.OrdinalIgnoreCase))
            {
                Response.Redirect("~/VipExclusive.aspx");
            }
        }
    }
}

In your .aspx markup, add the relevant controls:

<asp:HyperLink ID="lnkAdminPanel" runat="server" NavigateUrl="~/AdminPanel.aspx" Text="Admin Panel" Visible="False"></asp:HyperLink>
<asp:HyperLink ID="lnkUserDashboard" runat="server" NavigateUrl="~/UserDashboard.aspx" Text="User Dashboard"></asp:HyperLink>

2. 前端直接绑定 #

You can also use inline ASP.NET syntax to conditionally render content directly in your .aspx page:

<% if (User.Identity.IsAuthenticated) { %>
    <% 
        var emailClaim = ((System.Security.Claims.ClaimsPrincipal)User).FindFirst(System.Security.Claims.ClaimTypes.Email);
        string userEmail = emailClaim?.Value;
    %>
    <% if (!string.IsNullOrEmpty(userEmail) && userEmail.Equals("admin@yourdomain.com", StringComparison.OrdinalIgnoreCase)) { %>
        <a href="~/AdminPanel.aspx" class="admin-link">Admin Panel</a>
    <% } else { %>
        <a href="~/UserDashboard.aspx" class="user-link">User Dashboard</a>
    <% } %>
<% } %>

• 检查O365权限: 确保你的Azure AD应用注册拥有User.Read权限（Visual Studio通常会默认添加，但如果无法获取邮箱Claim，需要在Azure门户中验证并授予管理员同意）。
• 避免空引用异常: 始终为Claim添加空值检查——少数情况下用户的邮箱Claim可能未被填充。
• 用角色扩展管理: 对于大型应用，不要硬编码邮箱地址，建议将用户角色存储在与邮箱关联的数据库中，通过角色控制内容访问，这样更易于维护。

内容的提问来源于stack exchange，提问作者James Morrish