在ASP.NET Core 5应用程序中使用JWT令牌并使用Novell AD库进行身份验证的解决方案如下：

1. 在NuGet包管理器中添加以下依赖项： Microsoft.AspNetCore.Authentication.JwtBearer - 用于JWT身份验证 Novell.Directory.Ldap.NETStandard - 用于与AD进行身份验证的LDAP库

2. 在Startup.cs中配置身份验证服务：

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication(options =>
    {
        options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
        options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    })
    .AddJwtBearer(options =>
    {
        options.Authority = Configuration["Jwt:Issuer"];
        options.Audience = Configuration["Jwt:Audience"];
        options.RequireHttpsMetadata = false;

        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"])),
            ValidateIssuer = true,
            ValidIssuer = Configuration["Jwt:Issuer"],
            ValidateAudience = true,
            ValidAudience = Configuration["Jwt:Audience"],
            ClockSkew = TimeSpan.Zero
        };
    });

    services.AddSingleton(Configuration);
    services.AddSingleton();
    ...
}

3. 在应用程序中生成和验证JWT令牌：

private string GenerateJwtToken(User user)
{
    var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"]));
    var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256);

    var claims = new[]
    {
        new Claim(JwtRegisteredClaimNames.Sub, user.Username),
        new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
        new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
        new Claim(ClaimTypes.Role, "admin") // 从LDAP中获取用户角色并添加到此处
    };

    var token = new JwtSecurityToken(Configuration["Jwt:Issuer"],
                                      Configuration["Jwt:Audience"],
                                      claims,
                                      expires: DateTime.Now