how to create mvvm wpf validation on button click

See more:

WPF

MVVM

i have created validation but i want to show validation on button click ..in my application validation shown in if textbox is empty..i want show message in button ..

model

Category.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MVVMValidation.CustomValidationAttributes;
using MVVMValidation.Notification;


namespace BillingApplication.Model
{
    class Category : IDataErrorInfo, INotifyPropertyChanged
    {
        private short categoryId;
        private string categoryName;
        private string categoryCode;

        //[Unqiue(ErrorMessage = "Duplicate Id. Id already exists")]
        //[Required(ErrorMessage = "Id is Required")]

        public short CatogoryId
        {

            get
            {
                return CatogoryId;
            }
            set
            {
                CatogoryId = value;
            }
        }
        [Required(ErrorMessage = "Name is Required")]

        public string CategoryName
        {
            //get { return GetValue(() => CategoryName); }
            //set { SetValue(() => CategoryName, value); }
            get
            {
                return categoryName;
            }
            set
            {
                categoryName = value;
                NotifyPropertyChanged("CategoryName");
            }
        }

        protected void NotifyPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                // property changed
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
                // send app message (mvvm light toolkit)
                //if (message != null)
                //    message(this.IsValid);
            }
        }

        //private void NotifyPropertyChanged(string p)
        //{
        //    throw new NotImplementedException();
        //}

        //private string GetValue(Func<categoryName> func)
        //{
        //    throw new NotImplementedException();
        //}
         [Required(ErrorMessage = "cODE is Required")]
        public string CategoryCode
        {
             get
            {
                return categoryCode;
            }
            set
            {
                categoryCode = value;
                NotifyPropertyChanged("CategoryCode");
            }
        }


        #region IDataErrorInfo Members

        string IDataErrorInfo.Error
        {
            get
            {
                return null;
                //throw new NotImplementedException();
            }
        }

        string IDataErrorInfo.this[string propertyName]
        {
            get
            {
              return  GetValidationError(propertyName);
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion
        #region  Validation
        static readonly string[] ValidateProperties = { "CategoryName","CategoryCode" };
        public bool IsValid
        {
            get
            {
                foreach (string property in ValidateProperties)
                //{
                    if (GetValidationError(property) != null)
                            return false;

                    return true;
                //}
            }

        }
        string GetValidationError(string propertyName)
        {
            string error = null;
            switch (propertyName)
            {
                case "CategoryName":
                    error = ValidateCategoryName();
                    break;

            }
            switch (propertyName)
            {
                case "CategoryCode":
                    error = ValidateCategoryCode();
                    break;
            }
            return error;

        }

        private string ValidateCategoryCode()
        {
            if (string.IsNullOrWhiteSpace(CategoryCode))
            {
                return "Category code Cannot be empty";
            }
            return null;

        }
        private string ValidateCategoryName()
        {
            if (string.IsNullOrWhiteSpace(CategoryName))
            {
                return "Category Name Cannot be empty";
            }
            return null;

        }
        #endregion

    }
}

VIewModel


CategoryViewModel.cs

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Windows;
using System.Xml.Serialization;
using BillingApplication.Model;
using GalaSoft.MvvmLight;
using MVVMValidation.Commands;
using MVVMValidation.Notification;

namespace BillingApplication.ViewModel
{
    /// <summary>
    /// This class contains properties that a View can data bind to.
    /// <para>
    /// See http://www.galasoft.ch/mvvm
    /// </para>
    /// </summary>
    class CategoryViewModel : INotifyPropertyChanged
    {
        public CategoryViewModel()
        {
            Category = new Category
            {
                 CategoryName="",
                 CategoryCode=""
            };
        }
        public Category Category
        {
            get;
            set;
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

    }
}

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Windows;
using System.Xml.Serialization;
using BillingApplication.Model;
using GalaSoft.MvvmLight;
using MVVMValidation.Commands;
using MVVMValidation.Notification;

namespace BillingApplication.ViewModel
{
    /// <summary>
    /// This class contains properties that a View can data bind to.
    /// <para>
    /// See http://www.galasoft.ch/mvvm
    /// </para>
    /// </summary>
    class CategoryViewModel : INotifyPropertyChanged
    {
        public CategoryViewModel()
        {
            Category = new Category
            {
                 CategoryName="",
                 CategoryCode=""
            };
        }
        public Category Category
        {
            get;
            set;
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

    }
}

Category.xaml


<window x:class="BillingApplication.Views.Category" xmlns:x="#unknown">
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:ignore="http://www.ignore.com"
xmlns:model="clr-namespace:BillingApplication.Model"
xmlns:views="clr-namespace:BillingApplication.Views"
mc:Ignorable="d"

xmlns:local="clr-namespace:BillingApplication.ViewModel"
Title="Category" Width="867.164" Height="532.836">
<window.resources>

<!--

<window.resources>-->
<local:categoryviewmodel x:key="DataContext" xmlns:local="#unknown">



<grid datacontext="{StaticResource DataContext}" margin="10">

<textbox name="CategoryName" validation.errortemplate="{x:Null}">
Text="{Binding Category.CategoryName, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}"
HorizontalAlignment="Left" Height="75" Margin="53,36,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="259"/>
<Label Content="{Binding ElementName=CategoryName,Path=(Validation.Errors).CurrentItem.ErrorContent}" FontFamily="calibri" Foreground="Red" HorizontalAlignment="Left" Margin="400,63,0,0" VerticalAlignment="Top"/>
<Label Content="{Binding ElementName=CategoryCode,Path=(Validation.Errors).CurrentItem.ErrorContent}" FontFamily="calibri" Foreground="Red" HorizontalAlignment="Left" Margin="400,168,0,0" VerticalAlignment="Top" RenderTransformOrigin="7.533,0.823"/>
<textbox name="CategoryCode" validation.errortemplate="{x:Null}">
Text="{Binding Category.CategoryCode, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Height="39" Margin="53,168,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="259"/>

<!--<Label Content="{Binding ElementName=CategoryName,Path=(Validation.Errors).CurrentItem.ErrorContent}"/>-->




I want code for validation work in button click..pls help me