JWT无法将标头解码为Base64Url编码的字符串

我有以下代码:

public async Task<LoginResult> GenerateJwtTokenAsync(string email, string password)
{
    LoginResult loginResult = await _membershipProvider.Login(email, password);
    if (loginResult.Succeeded)
    {
        var symmetricKey = Convert.FromBase64String(Secret);

        var tokenDescriptor = new SecurityTokenDescriptor
        {
            Subject = new ClaimsIdentity(loginResult.Claims),
            Expires = DateTime.UtcNow.AddDays(1),
            SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(symmetricKey), SecurityAlgorithms.HmacSha256Signature)
        };

        var stoken = _tokenHandler.CreateToken(tokenDescriptor);
        var token = _tokenHandler.WriteToken(stoken);

        // Check token here to see if it works
        var jwtToken = _tokenHandler.ReadToken(token) as JwtSecurityToken;
        loginResult.JwtToken = token;
    }
    return loginResult;
}

public ClaimsPrincipal ValidateJwtToken(string tokenString)
{

    ClaimsPrincipal principal;

    try
    {
        var jwtToken = _tokenHandler.ReadToken(tokenString) as JwtSecurityToken;

        if (jwtToken == null)
        {
            principal = null;
        }
        else
        {
            var symmetricKey = Convert.FromBase64String(Secret);

            var validationParameters = new TokenValidationParameters()
            {
                RequireExpirationTime = true,
                ValidateIssuer = false,
                ValidateAudience = false,
                IssuerSigningKey = new SymmetricSecurityKey(symmetricKey)
            };

            SecurityToken securityToken;
            principal = _tokenHandler.ValidateToken(tokenString, validationParameters, out securityToken);
        }
    }
    catch (Exception ex)
    {
        principal = null;
    }

    return principal;
}

下面的行完美地读取了令牌，但是当我在第二种方法中实际读取它时，却出现了异常.

The line below reads the token perfectly, however when I actually read it in the 2nd method I get an exception.

// Check token here to see if it works
var jwtToken = _tokenHandler.ReadToken(token) as JwtSecurityToken

我已经验证了这两个字符串是相同的，当我实际上想在我的一生中验证令牌时，我看不到自己在做什么，对此我感到非常困惑.有什么想法吗?

I have verified the two string are identical, I am extremely confused as to why this stops working when I actually want to validate the token for the life of me I can't see what I am doing wrong. Any ideas please?

例外

   "IDX10729: Unable to decode the header 'header' as Base64Url encoded string. jwtEncodedString: 'Token here'."

堆栈跟踪:

   at System.IdentityModel.Tokens.Jwt.JwtSecurityToken.Decode(String[] tokenParts, String rawData)
   at System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler.ReadJwtToken(String token)
   at AuthService.ValidateJwtToken(String tokenString) in AuthService.cs:line 57