Traversing error messages stored in the Modelstate

In server-side validation, sometimes we add a modelerror, and then we need to return that information to the client as JS. Such as:

[HttpPost]        Public ActionResult Index (Logonmodel model)        {            if (string. IsNullOrEmpty (model. UserName)            {                modelstate.addmodelerror ("UserName", "Please enter the user name. ");                Return JavaScript ("alert (' Please enter username ')");            }            if (string. IsNullOrEmpty (model. PassWord)            {                modelstate.addmodelerror ("UserName", "Please enter a password. ");                Return JavaScript ("alert (' Please enter password ')");            }            if (string. IsNullOrEmpty (model. Checkcode)            {                modelstate.addmodelerror ("UserName", "Please enter the verification code. ");                Return JavaScript ("alert (' Please enter a verification code ')");            }            if (modelstate.isvalid)            {                Response.Write ("asdf");            }            return View ();        }

It is possible to rewrite this again, but it does the repetitive work, and if we can get the error message added in the Modelstate, we can save a lot of work.

The modelstate itself is a dictionary and stores information about validation failures. Specifically stored in modelstate.values[i]. ERRORS[J]. The ErrorMessage property.

The Errors property of Modelstate stores all validation failure information, is a modelerrorcollection type, Modelerrorcollection is a collection of Modelerror, The ErrorMessage property of Modelerror contains a validation failure error message.

This is roughly the case:

0ModelStateDictionary is actually idictionary<string, modelstate> type
The 0modelstate.errors property is actually a modelerrorcollection type
0ModelErrorCollection is actually a icollection<modelerror> type
The 0modelerror.errormessage property stores all validation failure information

The next task, in fact, is how to find out the verification information. We'll add a validation message by hand and try to display it:

Modelstate.addmodelerror ("UserName", "Please enter a user name.") "); return JavaScript (" alert (' "+ ModelState.Values.First ().) Errors[0]. ErrorMessage + "')");

In the above code, the values collection represents different key values, while errors represents different information under the same key value.

Modelstate.addmodelerror ("UserName", "Please enter a user name.") "); Modelstate.addmodelerror ("UserName", "User name is not correct.") "); Modelstate.addmodelerror ("PassWord", "Please enter the password.") "); Modelstate.addmodelerror ("PassWord", "Password is incorrect.") ");//outputs the first return Content (ModelState.Values.First (). Errors[0]. errormessage);//Output The second return Content (ModelState.Values.First (). ERRORS[1]. errormessage);//output Third return Content (ModelState.Values.Skip (1). First (). Errors[0]. errormessage);//output Fourth return Content (ModelState.Values.Skip (1). First (). ERRORS[1]. ErrorMessage);

Clearly, it is not difficult to traverse a modelstate.

                StringBuilder errinfo = new StringBuilder ();                foreach (var s in modelstate.values)                {                    foreach (var p in s.errors)                    {                        errinfo. AppendFormat ("{0}\\n", p.errormessage);                    }                }                Return JavaScript ("alert ('" + errinfo. ToString () + "')");

The following are the code that displays the error message centrally and displays the error message in turn:

Centralized display of error messages:

 [HttpPost] public actionresult Index (Logonmodel model) {if (string. IsNullOrEmpty (model. UserName) {modelstate.addmodelerror ("UserName", "Please enter the user name.            "); } if (string. IsNullOrEmpty (model. PassWord) {modelstate.addmodelerror ("PassWord", "Please enter a password.            "); } if (string. IsNullOrEmpty (model. Checkcode) {modelstate.addmodelerror ("Chkcode", "Please enter the verification code.            "); } if (!                Modelstate.isvalid) {StringBuilder errinfo = new StringBuilder ();                        foreach (var s in modelstate.values) {foreach (var p in s.errors) { Errinfo.                    AppendFormat ("{0}\\n", p.errormessage); }} return JavaScript ("alert ('" + errinfo.            ToString () + "')");        } return View (); }

Display the error message in turn:

[HttpPost]        Public ActionResult Index (Logonmodel model)        {            if (string. IsNullOrEmpty (model. UserName)            {                modelstate.addmodelerror ("UserName", "Please enter the user name. ");                Return JavaScript ("alert ('" + ModelState.Values.First ().) Errors[0]. ErrorMessage + "')");            }            if (string. IsNullOrEmpty (model. PassWord)            {                modelstate.addmodelerror ("UserName", "Please enter a password. ");                Return JavaScript ("alert ('" + ModelState.Values.First ().) Errors[0]. ErrorMessage + "')");            }            if (string. IsNullOrEmpty (model. Checkcode)            {                modelstate.addmodelerror ("UserName", "Please enter the verification code. ");                Return JavaScript ("alert ('" + ModelState.Values.First ().) Errors[0]. ErrorMessage + "')");            }            if (modelstate.isvalid)            {                            }            return View ();        }

Traversing error messages stored in the Modelstate