How to re-use the Action Method validation among multiple Controller classes

Question

i am working on an asp.net mvc-5 web application with entity framework-6.and i have mapped my DB tables using entity framework which generates a .edmx file containing a DBContext class. and currently i have two controller classes one for managing servers and the other for managing vms. When add/edit Server or VMs I want to check if their ip & mac addresses already exists. currently i am going these checks on the action method itself as follow:-

public class Server : Controller{
    [HttpPost]
     [ValidateAntiForgeryToken]
     public ActionResult Create(ServerJoin sj)
            {
                bool ITipunique = repository.ISITIPUnique(vmj.NetworkInfo2.FirstOrDefault().IPADDRESS);
                bool ITmacunique = repository.ISITMACUnique(vmj.NetworkInfo2.FirstOrDefault().MACADDRESS);
                bool Tipunique = repository.ISTIPUnique(vmj.NetworkInfo2.FirstOrDefault().IPADDRESS);
                bool Tmacunique = repository.ISTMACUnique(vmj.NetworkInfo2.FirstOrDefault().MACADDRESS);

                try
                {

                    if ((sj.IsIPUnique == true) && (!ITipunique || !Tipunique))
                    {

                        ModelState.AddModelError("NetworkInfo2[0].IPAddress", "Error occurred. The Same IP is already assigned.");

                    }
                    if ((sj.IsMACUnique == true) && (!ITmacunique || !Tmacunique))
                    {

                        ModelState.AddModelError("NetworkInfo2[0].MACAddress", "Error occurred. The Same MAC Address is already assigned.");

                    }

&

public class VM : Controlelr {    
    [HttpPost]
    [ValidateAntiForgeryToken]

            public ActionResult Create(VMJoin vmj)
            {

                bool ITipunique = repository.ISITIPUnique(vmj.NetworkInfo2.FirstOrDefault().IPADDRESS);
                bool ITmacunique = repository.ISITMACUnique(vmj.NetworkInfo2.FirstOrDefault().MACADDRESS);
                bool Tipunique = repository.ISTIPUnique(vmj.NetworkInfo2.FirstOrDefault().IPADDRESS);
                bool Tmacunique = repository.ISTMACUnique(vmj.NetworkInfo2.FirstOrDefault().MACADDRESS);
                try
                {
                    if ((vmj.IsIPUnique == true) && (!ITipunique || !Tipunique))
                    {

                        ModelState.AddModelError("NetworkInfo2[0].IPAddress", "Error occurred. The Same IP is already assigned.");

                    }
                    if ((vmj.IsMACUnique == true) && (!ITmacunique || !Tmacunique))
                    {

                        ModelState.AddModelError("NetworkInfo2[0].MACAddress", "Error occurred. The Same MAC Address is already assigned.");

                    }
                    if (!repository.IshypervisorServers(vmj.VirtualMachine.ServerID))
                    {
                        ModelState.AddModelError("VirtualMachine.ServerID", "Error occurred. Please select a valid hypervisor server. ");
                    }

this approach is working well, but i am facing a problem is that i have to repeat these validations on all the related action methods mainly (add & edit) and inside other controller classes (server, vms, storage device, etc...) so is there a way to manage the shared validation in a better way , which facilitate re-use and maintainability ?

EDIT

ServerJoin is as follow:-

public class ServerJoin : IValidatableObject
    {
        public Server Server { get; set; }
        public Resource Resource { get; set; }
        public Technology Technology { get; set; }
        public SDOrganization Site { get; set; }
        public SDOrganization Customer { get; set; }
        public NetworkInfo NetworkInfo { get; set; }
        public ICollection<NetworkInfo> NetworkInfo2 { get; set; }
        [Display(Name="Unique")]
        public bool IsMACUnique { get; set; }
        [Display(Name = "Unique")]
        public bool IsIPUnique { get; set; }
        public Nullable<double> SPEED { get; set; }
        public Nullable<Int64> PROCESSORCOUNT { get; set; }
        [Display(Name = "IP Unique")]
        public bool IsTIPUnique { get; set; }
        [Display(Name = "MAC Unique")]
        public bool IsTMACUnique { get; set; }
        public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
        {
            if (Server != null)
            {


                if (Server.RackUnitID != null && Server.RackID == null)
                {
                    yield return new ValidationResult("Please select a Rack, or remove the current Rack Unit", new[] { "Server.RackUnitID" });
                }
                if (Server.RackUnitIDTo != null && Server.RackUnitID == null)
                {
                    yield return new ValidationResult("Please select a Rack From Value", new[] { "Server.RackUnitID" });
                }
                if (Server.RackUnitIDTo != null && Server.RackUnitID != null && Server.RackUnitID > Server.RackUnitIDTo)
                {
                    yield return new ValidationResult("Rack Unit From must be less than or equal Rack Unit To", new[] { "Server.RackUnitID" });
                }


            }

&

 public class VMJoin
    {
         public VirtualMachine VirtualMachine { get; set; }
         public Resource Resource { get; set; }
         public Technology Technology { get; set; }
         public SDOrganization Site { get; set; }
         public SDOrganization Customer { get; set; }
         public NetworkInfo NetworkInfo { get; set; }
         public ICollection<NetworkInfo> NetworkInfo2 { get; set; }
         public ICollection<TechnologyIP> TechnologyIP { get; set; }
         [Display(Name = "Unique")]
         public bool IsMACUnique { get; set; }
         [Display(Name = "Unique")]
         public bool IsIPUnique { get; set; }
         public Nullable<double> SPEED { get; set; }
         public TechnologyIP TechnologyIP2 { get; set; }
         [Display(Name = "IP Unique")]
         public bool IsTIPUnique  { get; set; }
         [Display(Name = "MAC Unique")]
         public bool IsTMACUnique { get; set; }

    }
}

Answer 1

Start by creating a base class for your models with the common properties which will also reduce the code within the concrete classes.

public class BaseModel
{
    public bool IsIPUnique { get; set; }
    public bool IsMACUnique { get; set; }
    .... // other common properties
}
public class ServerJoin : BaseModel
{
    .... //  properties specific to ServerJoin 
}
public class VMJoin : BaseModel
{
    .... //  properties specific to VMJoin
}

and create a base controller for the common validation code

public class BaseController : Controller
{
    public void Validate(BaseModel model)
    {
        bool ITipunique = repository.ISITIPUnique(vmj.NetworkInfo2.FirstOrDefault().IPADDRESS);
        ....
        if ((model.IsIPUnique == true) && (!ITipunique || !Tipunique))
        {
            ModelState.AddModelError("NetworkInfo2[0].IPAddress", "Error occurred. The Same IP is already assigned.");
        }
        if ((model.IsMACUnique == true) && (!ITmacunique || !Tmacunique))
        {
            ModelState.AddModelError("NetworkInfo2[0].MACAddress", "Error occurred. The Same MAC Address is already assigned.");
        }
        .... // other common validation  
    }
}

and then on the specific controllers

public class ServerController : BaseController
{
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(ServerJoin sj)
    {
        Validate(sj); // adds the ModelStateErrors
        if (!ModelState.IsValid)
        {
            return View(sj);
        }
        ....
    }
}

public class VMController : BaseController
{
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(VMJoin vmj)
    {
        Validate(vmj); // adds the ModelStateErrors
        if (!ModelState.IsValid)
        {
            return View(vmj);
        }
        ....
    }
}

Answer 2

If VMJoin and ServerJoin have the same interface you can just create extension method with ModelState as a second parameter.

Update Here is example of extension method

    public static void TestMethod<T>(this T context, ModelStateDictionary modelsState) where T : YourDbBaseClass
    {
        //check context
        //add errors if exist
        modelsState.AddModelError("Error", "Big Error");
    }

    //Usage
    TestMethod<YourDbContext>(ModelState);

Answer 3

In my opinion the cleanest way to do this is using custom validation data annotation attribute.

You simply create custom attribute

public class IPUniqueValidator : ValidationAttribute
{
    public string ShouldCheck { get; set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value != null)
        {
            var IP = value.ToString();
            var isValid = false;

            // Using reflection to get the other property value 
            var shouldCheckPropert = validationContext.ObjectInstance.GetType().GetProperty(this.ShouldCheck);
            var shouldCheckPropertValue = (bool)shouldCheckPropert.GetValue(validationContext.ObjectInstance, null);
            if (shouldCheckPropertValue)
            {
                // do validation code...
            }

            if (isValid)
            {
                return ValidationResult.Success;
            }
            else
            {
                return new ValidationResult("Error occurred. The Same IP is already assigned.");
            }
        }
        else
        {
            return new ValidationResult("" + validationContext.DisplayName + " is required");
        }
    }
}

Mark your models with new attribute:

public class VMJoin
{
    [IPUniqueValidator(ShouldCheck = "ShouldCheck")]
    public string IpAddress { get; set; }

    public bool ShouldCheck { get; set; }
}

public class ServerJoin
{
    [IPUniqueValidator(ShouldCheck = "ShouldCheck")]
    public string IpAddress { get; set; }

    public bool ShouldCheck { get; set; }
}

And it left to you only add check for validation state. The framework will do all work for you.

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(ServerJoin sj)
{
    if (ModelState.IsValid)
    {
        // do staff 
    }
}

Answer 4

I would go with a custom ActionFilter . Check out how to access ModelState from an action filter here:

How do I access the ModelState from an ActionFilter?

You can also setup dependency injection within the custom action filter to receive the required repositories, further increasing testability/maintainability.