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] PublicActionResult Index (Logonmodel model) {if(string. IsNullOrEmpty (model. UserName)) {Modelstate.addmodelerror ("UserName","Please enter a user name. "); returnJavaScript ("alert (' Please enter user name ')"); }            if(string. IsNullOrEmpty (model. PassWord)) {Modelstate.addmodelerror ("UserName","Please enter a password. "); returnJavaScript ("alert (' Please enter password ')"); }            if(string. IsNullOrEmpty (model. Checkcode)) {Modelstate.addmodelerror ("UserName","Please enter a verification code. "); returnJavaScript ("alert (' Please enter verification code ')"); }            if(Modelstate.isvalid) {Response.Write ("asdf"); }            returnView (); }

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 the user name. "); return JavaScript ("alert ('" + ModelState.Values.First (). errors[0"')");

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","The user name is incorrect. "); Modelstate.addmodelerror ("PassWord","Please enter a password. "); Modelstate.addmodelerror ("PassWord","The password is not correct. ");//Output First articlereturnContent (ModelState.Values.First (). errors[0]. errormessage);//Output Second articlereturnContent (ModelState.Values.First (). errors[1]. errormessage);//Output Article IIIreturnContent (ModelState.Values.Skip (1). First (). errors[0]. errormessage);//Output FourthreturnContent (ModelState.Values.Skip (1). First (). errors[1]. ErrorMessage);

Clearly, it is not difficult to traverse a modelstate.

StringBuilder Errinfo =NewStringBuilder (); foreach(varSinchmodelstate.values) {foreach(varPinchs.errors) {Errinfo. AppendFormat ("{0}\\n", P.errormessage); }                }                returnJavaScript ("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] PublicActionResult Index (Logonmodel model) {if(string. IsNullOrEmpty (model. UserName)) {Modelstate.addmodelerror ("UserName","Please enter a user name. "); }            if(string. IsNullOrEmpty (model. PassWord)) {Modelstate.addmodelerror ("PassWord","Please enter a password. "); }            if(string. IsNullOrEmpty (model. Checkcode)) {Modelstate.addmodelerror ("Chkcode","Please enter a verification code. "); }            if(!modelstate.isvalid) {StringBuilder errinfo=NewStringBuilder (); foreach(varSinchmodelstate.values) {foreach(varPinchs.errors) {Errinfo. AppendFormat ("{0}\\n", P.errormessage); }                }                returnJavaScript ("alert ('"+ Errinfo. ToString () +"')"); }            returnView (); }

Display the error message in turn:

[HttpPost] PublicActionResult Index (Logonmodel model) {if(string. IsNullOrEmpty (model. UserName)) {Modelstate.addmodelerror ("UserName","Please enter a user name. "); returnJavaScript ("alert ('"+ ModelState.Values.First (). errors[0]. ErrorMessage +"')"); }            if(string. IsNullOrEmpty (model. PassWord)) {Modelstate.addmodelerror ("UserName","Please enter a password. "); returnJavaScript ("alert ('"+ ModelState.Values.First (). errors[0]. ErrorMessage +"')"); }            if(string. IsNullOrEmpty (model. Checkcode)) {Modelstate.addmodelerror ("UserName","Please enter a verification code. "); returnJavaScript ("alert ('"+ ModelState.Values.First (). errors[0]. ErrorMessage +"')"); }            if(modelstate.isvalid) {}returnView (); }

Traversing error messages stored in the Modelstate