Data annotation validation happening on page load in ASP.Net Core

Question

I am facing the issue of data validation being executed on load of a new page even though it is clearly coming from a Get method. Is there something that's triggering the validations on page load?

I have a button on a view to add a new Student record in the new screen:

View:

<a type="button" id="btnAddStudent" href='@Url.Action("Details","Student")' class="btn btn-tertiary" title="Add Student">Add Student</a>

The controller code for the Details action method in Student Controller is as follows.

[HttpGet]
public ActionResult Details(StudentInfo model)
{
    //This is populating the model parameters as expected.
    helper.StudentInfo(ref model);  
     return View(model);
}

The view for the Details screen is as follows. The page loads but is throwing validation errors even though it's a Get method.

<form id="frmSubmit" asp-action="Details" asp-controller="Student" method="post">
<input type="hidden" asp-for="StudentId" />

<div class="row">
    <div class="col-xs-12">
        @Html.ValidationSummary("", new { @class = "alert alert-danger validation" })
    </div>
</div>

<div class="row">
    <div class="col-xs-12">
        <div class="form-group">
            <label asp-for="Name">*StudentName</label><br />
            <input asp-for="Name" class="form-control" maxlength="100"  placeholder="Enter student name..." />
            <span asp-validation-for="Name" class="text-danger"></span>
        </div>
    </div>
</div>

<div class="row">
    <div class="col-xs-12">
        <div class="form-group">
            <label asp-for="AddressLine1"></label><br />
            <input asp-for="AddressLine1" class="form-control" placeholder="Enter address..." />
            <span asp-validation-for="AddressLine1" class="text-danger"></span>
        </div>
    </div>
</div>

<div class="row">
    <div class="col-xs-12">
        <div class="form-group">
            <label asp-for="AddressLine2"></label><br />
            <input asp-for="AddressLine2" class="form-control" maxlength="100" />
            <span asp-validation-for="AddressLine2" class="text-danger"></span>
        </div>
    </div>
</div>

<div class="box">
    <div class="form-group pull-right">           
        <button type="submit" class="btn btn-primary" value="save"> Save</button>
    </div>
</div>  

Is there something I am doing wrong? I have verified that the debug control goes to the Get method.There's alos no on load scripts which are doing any sort of validation.

Answer 1

1.Your get method contains the model parameter, when the request hit the method it will judge the ModelState by default. And when you hit the get method by your shared <a> , it send request without any data, so the ModelState is invalid.

2.Default Tag helper displays ModelState's value not Model.

In conclusion, you will render the ModelState error although it is a get method.

Two ways you can resolve this problem. The first way is that you can add ModelState.Clear() before you return View:

public ActionResult Details(StudentInfo model)
{
    ModelState.Clear();  //add this....
    helper.StudentInfo(ref model); 
            
    return View(model);
}

The second way is do not add the model as parameter:

public ActionResult Details()
{
    var model = new StudentInfo();
    helper.StudentInfo(ref model);
           
    return View(model);
}