Angular 2 form validation, minLength validator is not working

I have following Angular 2 form:

<register>
    <form [ngFormModel] = "registrationForm">
        <div class = "form-group">
            <label class = "control-label" for="email">Email</label>
            <input class = "form-control" type="email" id="email" ngControl="email" #email="ngForm">
        </div>
        <div *ngIf = "email.touched && email.errors">
            <div *ngIf = "!email.errors.required && email.errors.underscoreNotFound" class = "alert alert-danger">
                <span>Underscore is required</span> 
            </div>
            <div *ngIf = "email.errors.required" class = "alert alert-danger">
                <span>Email is required</span>
            </div>
        </div>
        <div class = "form-group">
            <label class = "control-label" for="password">Password</label>
            <input class = "form-control" type="password" id="password" ngControl="password" #password="ngForm">
        </div>
        <div *ngIf = "password.touched && password.errors">
            <div *ngIf = "password.errors.minLength && !password.errors.required" class = "alert alert-danger">
                <span>Password should contain 6 characters</span>
            </div>  
            <div *ngIf = "password.errors.required" class = "alert alert-danger">
                <span>Password is required</span>
            </div>          
        </div>
    </form>
</register>

This is my Component where I have implemented validators:

import {Component} from '@angular/core';
import {Control, ControlGroup, FormBuilder, Validators} from '@angular/common';
import {CustomValidator} from './CustomValidator';

@Component({
    selector: 'register',
    templateUrl: './app/authentication/register_validation/register.html',
})

export class RegisterComponent{
    registrationForm: ControlGroup;

    constructor(formBuilder:FormBuilder)
    {
        this.registrationForm = formBuilder.group({
            email: ['',Validators.compose([Validators.required, CustomValidator.underscore])], 
            password: ['',Validators.compose([Validators.required,Validators.minLength(6)])]
        });
    }

}

In this form, email field is working fine for both validators i.e. when I do not type anything , it gives "Email is required" message, when I start typing something, it gives "Underscore is required" message and when I type "_" all error messages disappears. However, when I try to apply such 2 validators on password field, it's not working. When I do not type password it gives message as "Password is required". But when I type something less than 6 characters, minLength message doesn't appear at all. What is wrong in this code?

The error key is minlength and not minLength:

<div *ngIf = "password.hasError('minlength') && !password.hasError('required')" class = "alert alert-danger">
  <span>Password should contain 6 characters</span>
</div>  

This really caught me out as well as I matched the key in my markup to what I had in code which is incorrect.

Sample Code

password1: ['', [Validators.required, Validators.minLength(8)]],

Sample Markup

*ngIf="registrationRequest.get('password1').hasError('minlength')"

Note in the code it's minlength entirely in lower case.

I was facing the same issue but after so many research I got a solution with this:
Use minlength instead of minLength
Here is the example:

<div *ngIf = "password.errors.minlength && !password.errors.required" class = "alert alert-danger">
      <span>Password should contain 6 characters</span>
    </div> 

Instead of:

<div *ngIf = "password.errors.minLength && !password.errors.required" class = "alert alert-danger">
  <span>Password should contain 6 characters</span>
</div>

I had the same problem where I wanted to validate a number field that contained the year, so I used Validators.maxLength(4) to make sure someone does not accidently type 5 numbers for a year. Turns out when you set the input type to number:

<input type="number" formControlName='year'>

then maxLength does not "work" anymore. Which actually makes sense if you think about it for half a second.

So I changed my date input to:

year: [null, [Validators.required, Validators.min(1990), Validators.max(2050)]],

Which is the right approach when working with a number field.