Re: Want to change the Validation attribute at runtime ASP.Net MVC - C# Discussion Boards

Re: Want to change the Validation attribute at runtime ASP.Net MVC

3-Aug-18 10:21

Not easily, but it can be done.

You're going to need to create a custom DataAnnotationsModelValidatorProvider, and modify the rules it returns.
validation - Possible to change Data Annotations during Runtime? (ASP.NET MVC's [Range] [Required] [StringLength] etc.) - Stack Overflow[^]

Eg:

public class CustomModelValidatorProvider : DataAnnotationsModelValidatorProvider
{
    protected override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
    {
        if (metadata.Model is ServiceFunctionCategoryLKP model && metadata.PropertyName == nameof(model.Code) && model.CodeLength >= 0)
        {
            var newAttributes = new List<Attribute>(attributes);
            var stringLength = newAttributes.OfType<StringLengthAttribute>().FirstOrDefault();
            if (stringLength != null)
            {
                newAttributes.Remove(stringLength);
                
                if (model.CodeLength != 0)
                {
                    newAttributes.Add(new StringLengthAttribute(model.CodeLength)
                    {
                        MinimumLength = model.CodeLength, 
                        ErrorMessage = $"The field {{0}} length must be at least {model.CodeLength}."
                    });
                }
                
                attributes = newAttributes;
            }
        }
        
        return base.GetValidators(metadata, context, attributes);
    }
}

ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add( new CustomValidatorProvider() );

NB: You're effectively allowing the user to override the validation rule by modifying a hidden field on the page. As a result, the validation can't really be trusted.

It would be better to create a separate model class for each required code length.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

indian1433-Aug-18 11:16

Re: Want to change the Validation attribute at runtime ASP.Net MVC

3-Aug-18 11:16

Just checking, is it going to remove all the other Validations that I have put on other classes?

Thanks,

Abdul Aleem

"There is already enough hatred in the world lets spread love, compassion and affection."

Richard Deeming3-Aug-18 12:14

Re: Want to change the Validation attribute at runtime ASP.Net MVC

3-Aug-18 12:14

No. It checks that the instance being validated is the specific model class; that the property being validated is the Code property; and it only replaces the StringLength validator on that property.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

indian1433-Aug-18 12:48

Re: Want to change the Validation attribute at runtime ASP.Net MVC

3-Aug-18 12:48

Hi Richard,

One last thing, I have created the method in the following way:

    public class CustomModelValidatorProvider : System.Web.Mvc.DataAnnotationsModelValidatorProvider
    {
        protected override IEnumerable<System.Web.Mvc.ModelValidator> GetValidators(System.Web.Mvc.ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
        { 
            if (metadata.Model is LookupTable)
            {
                LookupTable model = metadata.Model as LookupTable;

                if (metadata.PropertyName == GetPropertyName(() => model.CodeLength) && (model.CodeLength > 0))
                {
                    var newAttributes = new List<Attribute>(attributes);
                    var stringLength = newAttributes.OfType<StringLengthAttribute>().FirstOrDefault();
                    if (stringLength != null)
                    {
                        newAttributes.Remove(stringLength);

                        if (model.CodeLength != 0)
                        {
                            newAttributes.Add(new StringLengthAttribute(model.CodeLength)
                            {
                                MinimumLength = model.CodeLength,
                                ErrorMessage = @"The field {{0}} length must be at least {model.CodeLength}."
                            });
                        }

                        attributes = newAttributes;
                    }
                }
            }            

            return base.GetValidators(metadata, context, attributes);
        }

        public string GetPropertyName<T>(Expression<Func<T>> propertyLambda)
        {
            var me = propertyLambda.Body as MemberExpression;

            if (me == null)
            {
                throw new ArgumentException("You must pass a lambda of the form: '() => Class.Property' or '() => object.Property'");
            }

            return me.Member.Name;
        }
    }

can you please let me know how can I decorate or use it on my Model class, can you please give me that example, I am asking this question because this value is coming as null: metadata.PropertyName, so I am not able to compare with property name. So any help please?

thank you very very much buddy - as I said earlier have a Wonderful weekend with family and friends buddy.

Thanks,

Abdul Aleem

"There is already enough hatred in the world lets spread love, compassion and affection."

-- modified 3-Aug-18 19:53pm.

Richard Deeming6-Aug-18 2:05

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 2:05

You register the provider in Global.asax.cs:

ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add( new CustomValidatorProvider() );

I'd expect to see the PropertyName set to null for the class-level validation, but I'd expect the method to be called again for each property on the class.

You're currently checking whether the validators are for the CodeLength property; you need to customise the validators for the Code property instead.

if (metadata.PropertyName == GetPropertyName(() => model.Code) && ...

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

indian1436-Aug-18 6:39

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 6:39

ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add( new CustomValidatorProvider() );

I did this registration in the Global.asax.cs file, in the Application_Start() event.

And even if I changed the Condition to:

if (metadata.PropertyName == GetPropertyName(() => model.Code) && (model.CodeLength > 0))

Still I am getting the metadata.PropertyName null always, can you please suggest me what am I missing?

Just asking am I using any wrong namespace in references?, Because it was saying there is an ambiguous class names and those classes present in both the following namespaces using System.Web.ModelBinding; using System.Web.Mvc;
Am I using any wrong namespace or something like that kind of error, I am not understanding why is it giving metadata.PropertyName as null in all the cases?

Thanks,

Abdul Aleem

"There is already enough hatred in the world lets spread love, compassion and affection."

-- modified 6-Aug-18 13:01pm.

Richard Deeming6-Aug-18 7:15

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 7:15

Sorry, I picked the wrong property to test against. Replace metadata.Model with metadata.Container:

if (metadata.Model is ServiceFunctionCategoryLKP model && metadata.PropertyName == nameof(model.Code) && model.CodeLength >= 0)

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

indian1436-Aug-18 7:32

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 7:32

But still the attributes value in IEnumerable<attribute> attributes coming as null when I already have one Attribute on that class and when I try to expan the attributes collection object, it shows me "Enumeration yielded no results" in the end.

    public class LookupTable
    {
        public int Id { get; set; }

        [Required(ErrorMessage = "Code is required.")]<br />
        public string Code { get; set; }

        [Required(ErrorMessage = "Description is required.")]
        public string Description { get; set; }
        public int? ForeignKeyId { get; set; }
        public string ForeignKeyValue { get; set; }
        public DateTime? CreatedDate {get;set;} 
        public string CreatedBy {get;set;}       
        public int CodeLength { get; set; }
    }

Do I need to add anymore Attributes to the Code Property?, what am I missing here my friend?

Even after I changed my function to have Container instead of Model, still I get null at metadata.PropertyName

Always metadata.PropertyName is coming as null irrespective of any changes I do at if (metadata.PropertyName == GetPropertyName(() => model.Code) && (model.CodeLength > 0))
in the below function and attributes is also coming as null.

        protected override IEnumerable<System.Web.Mvc.ModelValidator> GetValidators(System.Web.Mvc.ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
        { 
            if (metadata.Model is LookupTable)
            {
                LookupTable model = metadata.Container as LookupTable;                

                if (metadata.PropertyName == GetPropertyName(() => model.Code) && (model.CodeLength > 0))
                {
                    var newAttributes = new List<Attribute>(attributes);
                    var stringLength = newAttributes.OfType<StringLengthAttribute>().FirstOrDefault();
                    if (stringLength != null)
                    {
                        newAttributes.Remove(stringLength);

                        if (model.CodeLength != 0)
                        {
                            newAttributes.Add(new StringLengthAttribute(model.CodeLength)
                            {
                                MinimumLength = model.CodeLength,
                                ErrorMessage = @"The field {{0}} length must be at least {model.CodeLength}."
                            });
                        }

                        attributes = newAttributes;
                    }
                }
            }            

            return base.GetValidators(metadata, context, attributes);
        }

Thanks,

Abdul Aleem

"There is already enough hatred in the world lets spread love, compassion and affection."

Richard Deeming6-Aug-18 9:16

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 9:16

I don't know what to suggest. I've tested the code, and it works. Confused | :confused:

If you're not putting a static StringLength attribute on the property, you'll need to the if (model.CodeLength != 0) block outside of the if (stringLength != null) block:

if (stringLength != null)
{
    newAttributes.Remove(stringLength);
}

if (model.CodeLength != 0)
{
    newAttributes.Add(new StringLengthAttribute(model.CodeLength)
    {
        MinimumLength = model.CodeLength,
        ErrorMessage = @"The field {{0}} length must be at least {model.CodeLength}."
    });
}

attributes = newAttributes;

But if you're never seeing a value in metadata.PropertyName, then there's something else going on.

I assume you have actually enabled unobtrusive validation?

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

indian1436-Aug-18 10:12

Re: Want to change the Validation attribute at runtime ASP.Net MVC

6-Aug-18 10:12

No I have not done this: unobtrusive validation, can you please let me know how to do it only on one particular class and property that I want.

Thanks,

Abdul Aleem

"There is already enough hatred in the world lets spread love, compassion and affection."

Richard Deeming7-Aug-18 1:56

When inputting data form main one other always on form main ?

7-Aug-18 1:56

You enable unobtrusive validation for the site in the web.config file:

XML

<configuration>
    <appSettings>
        <add key="ClientValidationEnabled" value="true"/>
        <add key="UnobtrusiveJavaScriptEnabled" value="true"/>

This should be included by default, but it depends on the template you started with.

Creating a MVC 3 Application with Razor and Unobtrusive JavaScript ⇒ Enabling Client-Side Validation[^]

I've created a minimal sample project in VS2017 which works as expected; you can download it from OneDrive[^].

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Member 24584672-Aug-18 21:29

Member 2458467

2-Aug-18 21:29

Suppose there are two forms: frmMain and frmPopup, frmPopup is always on frmMain, when select frmMain inputting data then frmPopup always on frmMain, frmPopup is always on frmMain, how is it to write code ? you see attach file http://www.mediafire.com/view/bq32fcb3ept329r/PopUpInput.jpg/file

Re: When inputting data form main one other always on form main ?

Richard MacCutchan2-Aug-18 21:40

Richard MacCutchan

2-Aug-18 21:40

Assuming that frmPopup is a dialog, you should only show it when you need to use it to communicate something to the user. Use the Form.ShowDialog() method so it does not stay on screen.

Re: When inputting data form main one other always on form main ?

OriginalGriff2-Aug-18 21:45

OriginalGriff

2-Aug-18 21:45

Set the popup forms TopMost property to true and use the Form.Show method instead of Form.ShowDialog

That way, it'll "float" above Form1, and you will still be able to enter data in the Form1 Textbox.

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Re: When inputting data form main one other always on form main ?

Member 24584675-Aug-18 16:42

Member 2458467

5-Aug-18 16:42

thank you very much.

Re: When inputting data form main one other always on form main ?

OriginalGriff5-Aug-18 19:35

OriginalGriff

5-Aug-18 19:35

You're welcome!

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Re: When inputting data form main one other always on form main ?

BillWoodruff3-Aug-18 2:17

BillWoodruff

3-Aug-18 2:17

You can set the 'Owner property of the pop-up Form to be the first Form ... which I assume is the Main Form. That will guarantee that when you show the pop-up, it will remain "above" the Main Form.

To get further assistance, I suggest you describe what your goal is in more detail: what is the relation of data the user enters on the Main Form to the what is displayed on the pop-up Form ?

«... thank the gods that they have made you superior to those events which they have not placed within your own control, rendered you accountable for that only which is within you own control For what, then, have they made you responsible? For that which is alone in your own power—a right use of things as they appear.» Discourses of Epictetus Book I:12

Jeremiah Okoduwa2-Aug-18 0:51

Jeremiah Okoduwa

2-Aug-18 0:51

As a beginner in CSharp, how do i differentiate between a class and a method. Thanks

Daniel Pfeffer2-Aug-18 1:12

Daniel Pfeffer

2-Aug-18 1:12

A class contains constructors, members, properties, and methods.

For example:

class Complex
{
    private double real;                // member #1
    private double imag;                // member #2

    // Constructors
    public Complex()
    {
        real = 0.0;
        imag = 0.0;
    }

    public Complex(double x)
    {
        real = x;
        imag = 0.0;
    }

    public Complex(double x, double y)
    {
        real = x;
        imag = y;
    }

    // property
    public double Real { get; set; }

    // method
    public double norm()
    {
        return real * real + imag * imag;
    }
};

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

Nathan Minier2-Aug-18 1:14

Nathan Minier

2-Aug-18 1:14

You might want to start with fundamentals. Firts: Google is your friend, i.e. learn to do some independent research.

There's an in-depth Object Oriented Design primer intended just for folks like you at:
Introduction to Object Oriented Programming Concepts (OOP) and More

"Never attribute to malice that which can be explained by stupidity."
- Hanlon's Razor

OriginalGriff2-Aug-18 1:19

OriginalGriff

2-Aug-18 1:19

Simple: a class starts with <public|private|protected|internal|protected internal> class followed by the class name.
A method starts with <public|private|protected|internal|protected internal> followed by the return type (or void) then the method name and a pair of brackets containing any parameters.

Plus, a method can only be defined inside a class, and not the other way round.

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Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Richard MacCutchan2-Aug-18 1:33

Richard MacCutchan

2-Aug-18 1:33

Here is a really good free book which should help to clarify things: .NET Book Zero by Charles Petzold[^]