C#•2y ago

❔ Help with record types and Ef Core

I have created an entity that uses several value objects. The value objects are all properties on the entity, and they are record types that contain validation login in the ctor, like so

public sealed record DisplayName
{
    private const long MAX_LENGTH = 255;
    public string Value { get; init; }

    public DisplayName(string name)
    {
        name ??= string.Empty;
        
        if (name.Length > MAX_LENGTH)
        {
            var error = DomainErrors.Common.MaxLengthExcceded(nameof(DisplayName), nameof(DisplayName), name, MAX_LENGTH);
            throw new DomainException(error);
        }

        Value = name;
    }

    public static implicit operator string(DisplayName name) => name.Value;
    public static implicit operator DisplayName(string name) => new(name);
    public override string ToString() => Value;
}

public sealed record DisplayName
{
    private const long MAX_LENGTH = 255;
    public string Value { get; init; }

    public DisplayName(string name)
    {
        name ??= string.Empty;
        
        if (name.Length > MAX_LENGTH)
        {
            var error = DomainErrors.Common.MaxLengthExcceded(nameof(DisplayName), nameof(DisplayName), name, MAX_LENGTH);
            throw new DomainException(error);
        }

        Value = name;
    }

    public static implicit operator string(DisplayName name) => name.Value;
    public static implicit operator DisplayName(string name) => new(name);
    public override string ToString() => Value;
}

The problem is that I run into this error when trying to build the Asp.net core app to generate a swagger json file

Unhandled exception. System.AggregateException: One or more errors occurred. (No suitable constructor was found for entity type 'DisplayName'. The following constructors had parameters that could not be bound to properties of the entity type: cannot bind 'name' in 'DisplayName(string name)'; cannot bind 'original' in 'DisplayName(DisplayName original)'.)

Unhandled exception. System.AggregateException: One or more errors occurred. (No suitable constructor was found for entity type 'DisplayName'. The following constructors had parameters that could not be bound to properties of the entity type: cannot bind 'name' in 'DisplayName(string name)'; cannot bind 'original' in 'DisplayName(DisplayName original)'.)

Here is a snippet of the ef core configuration for this property

builder.Property(r => r.DisplayName)
    .HasConversion(d => d.Value, d => new DisplayName(d))
    .IsRequired()
    .HasMaxLength(255)
    .HasColumnName("display_name");

builder.Property(r => r.DisplayName)
    .HasConversion(d => d.Value, d => new DisplayName(d))
    .IsRequired()
    .HasMaxLength(255)
    .HasColumnName("display_name");

Note: The entity class itself is a regular class. Not sure how to proceed from here. Any help is appreciated.

20 Replies

phaseshift•2y ago

Don't use db models for controller egress But maybe this will work if the param name exactly match

flow_stateOP•2y ago

For context, i'm using this example https://github.com/devmentors/MySpot/blob/master/src/MySpot.Infrastructure/DAL/Configurations/VehicleReservationConfiguration.cs as a guide, and I've seen this pattern replicated in various repos

GitHub

MySpot/VehicleReservationConfiguration.cs at master · devmentors/My...

Web API Fundamentals course project. Contribute to devmentors/MySpot development by creating an account on GitHub.

flow_stateOP•2y ago

One thing i've noticed is that my record objects all have another ctor that I did not create See the attached image. Looks like that is causing the confusion with ef core. But i dont know how to fix it

phaseshift•2y ago

Just change your main record ctor param name to match the property name

flow_stateOP•2y ago

I changed the records param name to displayname, but it unfortunately didn't help. I still get same error

phaseshift•2y ago

But the property name is Value

flow_stateOP•2y ago

I tried that and got an error error CS0542: 'DisplayName': member names cannot be the same as their enclosing type

phaseshift•2y ago

That's not what I said

flow_stateOP•2y ago

did you mean change the ctor param name to value to match the Value property?

phaseshift•2y ago

That is what I said

flow_stateOP•2y ago

Sorry for the misunderstanding, but I tried that as well and got same error

Unhandled exception. System.AggregateException: One or more errors occurred. (No suitable constructor was found for entity type 'DisplayName'. The following constructors had parameters that could not be bound to properties of the entity type: cannot bind 'value' in 'DisplayName(string value)'; cannot bind 'original' in 'DisplayName(DisplayName original)'.)

phaseshift•2y ago

That copy ctor is not present in the repo you linked to Is it because your don't have a primary ctor like in that repo as well? What version EF core are you on?

flow_stateOP•2y ago

6.0.13. This is a .NET6 app sorry i'm using Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="6.0.8"

phaseshift•2y ago

You might need net7 to use binding to init; properties

flow_stateOP•2y ago

🤔... I guess i'll have to look into that but thanks for your help either way

phaseshift•2y ago

Your linked repo is net6, I checked But their properties are get only, not init But they do have the record DName(string val) syntax

flow_stateOP•2y ago

My guess is that the implicit operators on the record type is the cause. I use it as a convenient way to map from a string to the record type without invoking new all over the place

phaseshift•2y ago

No, don't think so

flow_stateOP•2y ago

Actually you're right. It should not convert since i'm passing the value in via the ctor in the ef core value converter Still a head scratcher though

Accord•2y ago

Looks like nothing has happened here. I will mark this as stale and this post will be archived until there is new activity.

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❔ Help with record types and Ef Core