How to display validation error message for Textbox

Question

 display validation error message for Textbox "NumberOfPeriods"

 

Error Msg : 'The ViewData item that has the key 'MethodCode' is of type 'System.String' but must be of type 'IEnumerable<SelectListItem>'.' 

 

public class AssetBasisRuleViewModel

{

   [DisplayName("Number of periods")]

   public int? NumberOfPeriods { get; set; }

} 

 

 

public sealed class AssetBasisRuleMethod : SmartCodes

{

public AssetBasisRuleMethod() { }

private AssetBasisRuleMethod(String meaning, String smartCode) : base(meaning, smartCode, "AssetBasisRuleMethod") { }

public static AssetBasisRuleMethod P { get { return new AssetBasisRuleMethod("Point-in-time", "P"); } }

public static AssetBasisRuleMethod A { get { return new AssetBasisRuleMethod("Average", "A"); } }

public static AssetBasisRuleMethod D { get { return new AssetBasisRuleMethod("ADB", "D"); } }

public static AssetBasisRuleMethod AA { get { return new AssetBasisRuleMethod("Average-of-averages", "AA"); } }

}

 

 

[HttpPost]

[ValidateAntiForgeryToken]

public ActionResult Create(AssetBasisRuleViewModel model)

{

using (var dbContextScope = _dbContextScopeFactory.Create())

{

User user = _Login.GetCurrentUser();

if (!ModelState.IsValid)

{

model.PrepareSelectLists();

return View(model);

}

// Conditional validations

if (model.MethodCode == AssetBasisRuleMethod.A.SmartCode)

{

if (model.NumberOfPeriods == null)

{

ModelState.AddModelError("NumberOfPeriods", "The number of periods are required for averaging methods.");

return View(model);

}

}

else if (model.MethodCode == AssetBasisRuleMethod.AA.SmartCode)

{

model.NumberOfPeriods = 3;

}

else if (model.MethodCode == AssetBasisRuleMethod.P.SmartCode)

{

model.AveragePeriodCode = "P"; // Set to Period for non-average (not settable in UI)

}

// Default to "all" in period for valuation query when the rule type is ADB

else if (model.MethodCode == AssetBasisRuleMethod.D.SmartCode)

{

model.DateInPeriodCode = AssetBasisRuleDateInPeriod.A.SmartCode;

}

 _repo.AddAssetBasisRule(abr, user);

dbContextScope.SaveChanges();

}

return RedirectToAction("Index");

}