How to properly configure lazy loading

In the view model below, I can see that part.CountryCode is always null.

I can get the data if I use db.Parts.Include(p => p.CountryCode), but I would like to set up lazy loading for now. Does anyone know what I'm missing?

I'm using:

Microsoft.EntityFrameworkCore (2.1.4) in a NETStandard.Library(2.0.3)

UI is WPF with .NET 4.6.1

ViewModel

class PagePartsViewModel : BaseViewModel

{

    public ObservableCollection<PartViewModel> Parts { get; set; }



    public PagePartsViewModel()

    {

        Parts = new ObservableCollection<PartViewModel>();

        var parts = StandardDatabase.Commands.GetParts();

        foreach (var part in parts)

        {

            Parts.Add(new PartViewModel(part));

        }

    }

}

GetParts()

public static List<Part> GetParts()

{

    using (var db = new ApplicationDbContext())

    {

        return db.Parts.ToList();

    }

}

ApplicationDbContext.OnConfiguring()

optionsBuilder

    .UseLazyLoadingProxies()

    .UseSqlServer("Connection String");

ApplicationDbContext.OnModelCreating()

builder.Entity<Part>()

    .HasOne(p => p.CountryCode);

builder.Entity<CountryCode>()

    .HasAlternateKey(cc => cc.Code);

Part.cs

public class Part : EntityBase

{

    public string OEMNumber { get; set; }

    public string Description { get; set; }

    public string CountryOfOrigin { get; set; }

    [Column(TypeName = "decimal(10, 2)")]

    public decimal BellUnitCost { get; set; }

    [Column(TypeName = "decimal(9, 3)")]

    public double Weight { get; set; }



    public virtual StockQuantity StockQuantity { get; set; }

    public virtual ICollection<PartQuantity> PartQuantities { get; set; }



    public virtual CountryCode CountryCode { get; set; }

}

CountryCode.cs

public class CountryCode : EntityBase

{

    public string Code { get; set; }

    public string FriendlyName { get; set; }



    public virtual ICollection<Part> Parts { get; set; }

}

asked Nov 24 '18 at 14:07

Bassie

3,9322051

add a comment |

In the view model below, I can see that part.CountryCode is always null.

I can get the data if I use db.Parts.Include(p => p.CountryCode), but I would like to set up lazy loading for now. Does anyone know what I'm missing?

I'm using:

Microsoft.EntityFrameworkCore (2.1.4) in a NETStandard.Library(2.0.3)

UI is WPF with .NET 4.6.1

ViewModel

class PagePartsViewModel : BaseViewModel

{

    public ObservableCollection<PartViewModel> Parts { get; set; }



    public PagePartsViewModel()

    {

        Parts = new ObservableCollection<PartViewModel>();

        var parts = StandardDatabase.Commands.GetParts();

        foreach (var part in parts)

        {

            Parts.Add(new PartViewModel(part));

        }

    }

}

GetParts()

public static List<Part> GetParts()

{

    using (var db = new ApplicationDbContext())

    {

        return db.Parts.ToList();

    }

}

ApplicationDbContext.OnConfiguring()

optionsBuilder

    .UseLazyLoadingProxies()

    .UseSqlServer("Connection String");

ApplicationDbContext.OnModelCreating()

builder.Entity<Part>()

    .HasOne(p => p.CountryCode);

builder.Entity<CountryCode>()

    .HasAlternateKey(cc => cc.Code);

Part.cs

public class Part : EntityBase

{

    public string OEMNumber { get; set; }

    public string Description { get; set; }

    public string CountryOfOrigin { get; set; }

    [Column(TypeName = "decimal(10, 2)")]

    public decimal BellUnitCost { get; set; }

    [Column(TypeName = "decimal(9, 3)")]

    public double Weight { get; set; }



    public virtual StockQuantity StockQuantity { get; set; }

    public virtual ICollection<PartQuantity> PartQuantities { get; set; }



    public virtual CountryCode CountryCode { get; set; }

}

CountryCode.cs

public class CountryCode : EntityBase

{

    public string Code { get; set; }

    public string FriendlyName { get; set; }



    public virtual ICollection<Part> Parts { get; set; }

}

asked Nov 24 '18 at 14:07

Bassie

3,9322051

add a comment |

In the view model below, I can see that part.CountryCode is always null.

I can get the data if I use db.Parts.Include(p => p.CountryCode), but I would like to set up lazy loading for now. Does anyone know what I'm missing?

I'm using:

Microsoft.EntityFrameworkCore (2.1.4) in a NETStandard.Library(2.0.3)

UI is WPF with .NET 4.6.1

ViewModel

class PagePartsViewModel : BaseViewModel

{

    public ObservableCollection<PartViewModel> Parts { get; set; }



    public PagePartsViewModel()

    {

        Parts = new ObservableCollection<PartViewModel>();

        var parts = StandardDatabase.Commands.GetParts();

        foreach (var part in parts)

        {

            Parts.Add(new PartViewModel(part));

        }

    }

}

GetParts()

public static List<Part> GetParts()

{

    using (var db = new ApplicationDbContext())

    {

        return db.Parts.ToList();

    }

}

ApplicationDbContext.OnConfiguring()

optionsBuilder

    .UseLazyLoadingProxies()

    .UseSqlServer("Connection String");

ApplicationDbContext.OnModelCreating()

builder.Entity<Part>()

    .HasOne(p => p.CountryCode);

builder.Entity<CountryCode>()

    .HasAlternateKey(cc => cc.Code);

Part.cs

public class Part : EntityBase

{

    public string OEMNumber { get; set; }

    public string Description { get; set; }

    public string CountryOfOrigin { get; set; }

    [Column(TypeName = "decimal(10, 2)")]

    public decimal BellUnitCost { get; set; }

    [Column(TypeName = "decimal(9, 3)")]

    public double Weight { get; set; }



    public virtual StockQuantity StockQuantity { get; set; }

    public virtual ICollection<PartQuantity> PartQuantities { get; set; }



    public virtual CountryCode CountryCode { get; set; }

}

CountryCode.cs

public class CountryCode : EntityBase

{

    public string Code { get; set; }

    public string FriendlyName { get; set; }



    public virtual ICollection<Part> Parts { get; set; }

}

asked Nov 24 '18 at 14:07

Bassie

3,9322051

In the view model below, I can see that part.CountryCode is always null.

I can get the data if I use db.Parts.Include(p => p.CountryCode), but I would like to set up lazy loading for now. Does anyone know what I'm missing?

I'm using:

Microsoft.EntityFrameworkCore (2.1.4) in a NETStandard.Library(2.0.3)

UI is WPF with .NET 4.6.1

ViewModel

class PagePartsViewModel : BaseViewModel

{

    public ObservableCollection<PartViewModel> Parts { get; set; }



    public PagePartsViewModel()

    {

        Parts = new ObservableCollection<PartViewModel>();

        var parts = StandardDatabase.Commands.GetParts();

        foreach (var part in parts)

        {

            Parts.Add(new PartViewModel(part));

        }

    }

}

GetParts()

public static List<Part> GetParts()

{

    using (var db = new ApplicationDbContext())

    {

        return db.Parts.ToList();

    }

}

ApplicationDbContext.OnConfiguring()

optionsBuilder

    .UseLazyLoadingProxies()

    .UseSqlServer("Connection String");

ApplicationDbContext.OnModelCreating()

builder.Entity<Part>()

    .HasOne(p => p.CountryCode);

builder.Entity<CountryCode>()

    .HasAlternateKey(cc => cc.Code);

Part.cs

public class Part : EntityBase

{

    public string OEMNumber { get; set; }

    public string Description { get; set; }

    public string CountryOfOrigin { get; set; }

    [Column(TypeName = "decimal(10, 2)")]

    public decimal BellUnitCost { get; set; }

    [Column(TypeName = "decimal(9, 3)")]

    public double Weight { get; set; }



    public virtual StockQuantity StockQuantity { get; set; }

    public virtual ICollection<PartQuantity> PartQuantities { get; set; }



    public virtual CountryCode CountryCode { get; set; }

}

CountryCode.cs

public class CountryCode : EntityBase

{

    public string Code { get; set; }

    public string FriendlyName { get; set; }



    public virtual ICollection<Part> Parts { get; set; }

}

c# .net-core entity-framework-core lazy-loading .net-standard

asked Nov 24 '18 at 14:07

Bassie

3,9322051

asked Nov 24 '18 at 14:07

Bassie

3,9322051

asked Nov 24 '18 at 14:07

Bassie

3,9322051

asked Nov 24 '18 at 14:07

Bassie

3,9322051

asked Nov 24 '18 at 14:07

Bassie

3,9322051

add a comment |

1 Answer
1

active

oldest

votes

using (var db = new ApplicationDbContext())

{

    return db.Parts.ToList();

}

The using block disposes your dbContext once it finishes loading your parts. Lazy-loading requires the dbContext to still be alive.

answered Nov 24 '18 at 14:25

Brad M

7,11111633

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

add a comment |

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1 Answer
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1 Answer
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oldest

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using (var db = new ApplicationDbContext())

{

    return db.Parts.ToList();

}

The using block disposes your dbContext once it finishes loading your parts. Lazy-loading requires the dbContext to still be alive.

answered Nov 24 '18 at 14:25

Brad M

7,11111633

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

add a comment |

using (var db = new ApplicationDbContext())

{

    return db.Parts.ToList();

}

The using block disposes your dbContext once it finishes loading your parts. Lazy-loading requires the dbContext to still be alive.

answered Nov 24 '18 at 14:25

Brad M

7,11111633

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

add a comment |

using (var db = new ApplicationDbContext())

{

    return db.Parts.ToList();

}

The using block disposes your dbContext once it finishes loading your parts. Lazy-loading requires the dbContext to still be alive.

answered Nov 24 '18 at 14:25

Brad M

7,11111633

using (var db = new ApplicationDbContext())

{

    return db.Parts.ToList();

}

The using block disposes your dbContext once it finishes loading your parts. Lazy-loading requires the dbContext to still be alive.

answered Nov 24 '18 at 14:25

Brad M

7,11111633

answered Nov 24 '18 at 14:25

Brad M

7,11111633

answered Nov 24 '18 at 14:25

Brad M

7,11111633

answered Nov 24 '18 at 14:25

Brad M

7,11111633

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

add a comment |

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

Thanks Brad that makes sense - I didn't know it worked like that. Would you recommend that Commands implements IDisposable so that I can wrap GetParts() in a using Commands()?

– Bassie
Nov 24 '18 at 14:30

Personally I would recommend just including any navigation properties you need ahead of time. I suggest using dependency injection and having your class accept an instance of dbContext and then scoping the lifetime of the dbContext to the lifetime of the request (I'm not sure how that works with WPF, but the dbContext lifetime shouldn't be the responsibility of your NetStandard library)

– Brad M
Nov 24 '18 at 14:36

I would like to try that but I'm not sure how I can inject a .net-core DbContext into a .net-framework app

– Bassie
Nov 24 '18 at 14:42

add a comment |

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