Mvc model binding, missing one field when save

Question

0.00/5 (No votes)

See more:

Say I use model binding in MVC.

public ActionResult Edit(MyModel model)
{
    db.SaveChanges();
    return View(model);
}

When we pass the model, we miss one field in the model.
What will happen if we save it to db?

What I have tried:

Not sure but I guess

It depends if the field that you forgot to set is mandatory or not.

Posted 13-Aug-17 4:06am

Member 12658724

Updated 15-Aug-17 9:40am

Add a Solution

Comments

Kornfeld Eliyahu Peter 15-Aug-17 6:34am

What do you mean by 'we miss one field in the model'?

Member 12658724 15-Aug-17 8:31am

Say we have a class people. It has two properties, name and age. When we pass the instance of people, we only supply the age. We forget to supply the name in the model.

Kornfeld Eliyahu Peter 15-Aug-17 8:38am

It depends on how it declared in the SQL, if it is NULLABLE it will succeed, otherwise will fail...

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Accepted Answer · 2017-08-15T09:40:00

Based on the code you've posted, it won't do anything at all. There's no code to update the database from the posted data, so the database won't be updated.

You'll need to start by retrieving the corresponding entity from the database:

C#

var entity = db.YourSet.Find(model.PrimaryKey);
if (entity == null) return RedirectToAction("Index");

You'll then need to copy the values from the posted data. You can either do that manually:

entity.Prop1 = model.Prop1;
entity.Prop2 = model.Prop2;
...

Or you can use the TryUpdateModel[^] method. But you'll want to explicitly state which properties can be updated, to prevent a malicious user from overwriting things that shouldn't be changed:

C#

TryUpdateModel(entity, new[] { "Prop1", "Prop2", ... });

Once you've done that, then you can save the changes:

C#

db.SaveChanges();
return View(model);

If you don't copy a property from the posted data, or don't include it in the list of included properties, then the database value will not be changed.

If you copy / include the property, but the user didn't enter a value, then the database value will be cleared. If the property is required, you'll get a validation error when you try to save. Otherwise, the value in the database will be overwritten.