Generate a Zendesk Messaging JWT in .Net and login the user on the client side.

app.js

zE("messenger", "loginUser", (callback) => callback(token));

JwtTokenGenerator.cs

using System;
using System.IdentityModel.Tokens.Jwt;
using Microsoft.IdentityModel.Tokens;
using System.Text;

public class JwtTokenGenerator
{
    public string CreateZendeskJwtToken(string zendeskSecret, string keyId, string userName, string userEmail, string externalId)
    {
        var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(zendeskSecret));
        var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256);

        var header = new JwtHeader(credentials);
        //keyId is required by Zendesk - need to generate from wagepoint admin interface + secret
        //Zendesk messaging SDK requires name, email, external_id, and scope
        header.Add("kid", keyId);
        // Add required claims
        var payload = new JwtPayload
        {

            {"name", userName},
            {"email", userEmail},
            {"external_id", externalId},
            {"scope", "user"},
            { "iat", DateTimeOffset.UtcNow.ToUnixTimeSeconds() },
            { "exp", DateTimeOffset.UtcNow.AddMinutes(15).ToUnixTimeSeconds() } // Token expiry time 
            //can add more claims as necessary

        };

        // Create the JWT token
        var token = new JwtSecurityToken(header, payload);
        return new JwtSecurityTokenHandler().WriteToken(token);
    }
}