public class SimpleAuthorizationServerProvider : OAuthAuthorizationServerProvider
{
    public override async Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
    {
        context.Validated();
    }
    public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
    {
        context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" });
        bool isLogin = false;
        using (DAL.HesabgarClubEntities db = new HesabgarClubEntities())
        {
            string hashpass = hashMaker.HashPassword(context.Password);
          isLogin= db.AspNetUsers.Any(m => m.UserName == context.UserName && m.PasswordHash.Equals(hashpass));
          if (!isLogin)
          {
              context.SetError("invalid_grant", "The user name or password is incorrect." + hashpass);
              return;
          }
        }
        var identity = new ClaimsIdentity(context.Options.AuthenticationType);
        identity.AddClaim(new Claim("sub", context.UserName));
        identity.AddClaim(new Claim("role", "user"));
        context.Validated(identity);
    }
}

public class hashMaker
{
    public static bool VerifyHashedPassword(string hashedPassword, string password)
    {
        byte[] buffer4;
        if (hashedPassword == null)
        {
            return false;
        }
        if (password == null)
        {
            throw new ArgumentNullException("password");
        }
        byte[] src = Convert.FromBase64String(hashedPassword);
        if ((src.Length != 0x31) || (src[0] != 0))
        {
            return false;
        }
        byte[] dst = new byte[0x10];
        Buffer.BlockCopy(src, 1, dst, 0, 0x10);
        byte[] buffer3 = new byte[0x20];
        Buffer.BlockCopy(src, 0x11, buffer3, 0, 0x20);
        using (Rfc2898DeriveBytes bytes = new Rfc2898DeriveBytes(password, dst, 0x3e8))
        {
            buffer4 = bytes.GetBytes(0x20);
        }
        return ByteArrayCompare(buffer3, buffer4);
    }

    static bool ByteArrayCompare(byte[] a1, byte[] a2)
    {
        return StructuralComparisons.StructuralEqualityComparer.Equals(a1, a2);
    }
    public static string HashPassword(string password)
    {
        byte[] salt;
        byte[] buffer2;
        if (password == null)
        {
            throw new ArgumentNullException("password");
        }
        using (Rfc2898DeriveBytes bytes = new Rfc2898DeriveBytes(password, 0x10, 0x3e8))
        {
            salt = bytes.Salt;
            buffer2 = bytes.GetBytes(0x20);
        }
        byte[] dst = new byte[0x31];
        Buffer.BlockCopy(salt, 0, dst, 1, 0x10);
        Buffer.BlockCopy(buffer2, 0, dst, 0x11, 0x20);
        return Convert.ToBase64String(dst);
    }
}