Store Lambda expressions as variable

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2
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Is it possible to store a lambda expression as a variable and use it in multiple places.
My db objects have an Id as int and a UId as an uniqueidentifier and I have to write very similar expressions when selecting based on Id or UId.

Lambda:

var result = await this.Worker.GetRepo<Category>().DbSet

    .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules)

    .SingleAsync(cat => cat.Id.Equals(id));

Is it possible to:

var expression = .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules);

then use the variable like:

await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.Id.Equals(id));



await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.UId.Equals(uid));

I know the syntax is wrong, it's just what I'm looking for.

asked Nov 19 '17 at 0:58

TheRuler

404219

You may want to look at Func<T, TResult> (msdn.microsoft.com/en-us/library/bb549151(v=vs.110).aspx) which should allow you to do what you want.
– Chris
Nov 19 '17 at 1:16

1

@Chris, Or sometimes Expression<>, that is Expression<Func<T, TResult>>, since some flavors of Linq need an expression tree, to be translated into e.g. SQL, and cannot use a plain .NET delegate instance.
– Jeppe Stig Nielsen
Nov 11 at 11:17

add a comment |

up vote
2
down vote

favorite

Lambda:

var result = await this.Worker.GetRepo<Category>().DbSet

    .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules)

    .SingleAsync(cat => cat.Id.Equals(id));

Is it possible to:

var expression = .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules);

then use the variable like:

await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.Id.Equals(id));



await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.UId.Equals(uid));

I know the syntax is wrong, it's just what I'm looking for.

asked Nov 19 '17 at 0:58

TheRuler

404219

You may want to look at Func<T, TResult> (msdn.microsoft.com/en-us/library/bb549151(v=vs.110).aspx) which should allow you to do what you want.
– Chris
Nov 19 '17 at 1:16

1

@Chris, Or sometimes Expression<>, that is Expression<Func<T, TResult>>, since some flavors of Linq need an expression tree, to be translated into e.g. SQL, and cannot use a plain .NET delegate instance.
– Jeppe Stig Nielsen
Nov 11 at 11:17

add a comment |

up vote
2
down vote

favorite

Lambda:

var result = await this.Worker.GetRepo<Category>().DbSet

    .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules)

    .SingleAsync(cat => cat.Id.Equals(id));

Is it possible to:

var expression = .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules);

then use the variable like:

await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.Id.Equals(id));



await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.UId.Equals(uid));

I know the syntax is wrong, it's just what I'm looking for.

asked Nov 19 '17 at 0:58

TheRuler

404219

Lambda:

var result = await this.Worker.GetRepo<Category>().DbSet

    .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules)

    .SingleAsync(cat => cat.Id.Equals(id));

Is it possible to:

var expression = .Include(cat => cat.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.InfoItems)

    .Include(cat => cat.Products)

        .ThenInclude(prd => prd.GraphicItems)

            .ThenInclude(itm => itm.Graphic)

                .ThenInclude(gfx => gfx.Items)

    .Include(cat => cat.GraphicItems)

        .ThenInclude(gfx => gfx.Graphic)

            .ThenInclude(gfx => gfx.Items)

    .Include(m => m.Modules);

then use the variable like:

await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.Id.Equals(id));



await this.Worker.GetRepo<Category>().expression.SingleAsync(cat => cat.UId.Equals(uid));

I know the syntax is wrong, it's just what I'm looking for.

c# entity-framework lambda entity-framework-core

asked Nov 19 '17 at 0:58

TheRuler

404219

asked Nov 19 '17 at 0:58

TheRuler

404219

asked Nov 19 '17 at 0:58

TheRuler

404219

asked Nov 19 '17 at 0:58

TheRuler

404219

asked Nov 19 '17 at 0:58

TheRuler

404219

You may want to look at Func<T, TResult> (msdn.microsoft.com/en-us/library/bb549151(v=vs.110).aspx) which should allow you to do what you want.
– Chris
Nov 19 '17 at 1:16

1

@Chris, Or sometimes Expression<>, that is Expression<Func<T, TResult>>, since some flavors of Linq need an expression tree, to be translated into e.g. SQL, and cannot use a plain .NET delegate instance.
– Jeppe Stig Nielsen
Nov 11 at 11:17

add a comment |

You may want to look at Func<T, TResult> (msdn.microsoft.com/en-us/library/bb549151(v=vs.110).aspx) which should allow you to do what you want.
– Chris
Nov 19 '17 at 1:16

1

@Chris, Or sometimes Expression<>, that is Expression<Func<T, TResult>>, since some flavors of Linq need an expression tree, to be translated into e.g. SQL, and cannot use a plain .NET delegate instance.
– Jeppe Stig Nielsen
Nov 11 at 11:17

You may want to look at Func<T, TResult> (msdn.microsoft.com/en-us/library/bb549151(v=vs.110).aspx) which should allow you to do what you want.
– Chris
Nov 19 '17 at 1:16

@Chris, Or sometimes Expression<>, that is Expression<Func<T, TResult>>, since some flavors of Linq need an expression tree, to be translated into e.g. SQL, and cannot use a plain .NET delegate instance.
– Jeppe Stig Nielsen
Nov 11 at 11:17

add a comment |

1 Answer
1

active

oldest

votes

up vote
3
down vote

accepted

You can just create a method that returns an IQueryable<Category>. If you want the usage to be the same as your example then this could be an extension method:

public static IQueryable<Category> GetExpression(this IQueryable<Category> qry)

{

    var expression = qry.Include(cat => cat.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.GraphicItems)

                .ThenInclude(itm => itm.Graphic)

                    .ThenInclude(gfx => gfx.Items)

        .Include(cat => cat.GraphicItems)

            .ThenInclude(gfx => gfx.Graphic)

                .ThenInclude(gfx => gfx.Items)

        .Include(m => m.Modules);



    return expression;

}

You can then use this as follows:

await this.Worker

    .GetRepo<Category>()

    .GetExpression()

    .SingleAsync(cat => cat.UId.Equals(uid));

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

1

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
3
down vote

accepted

You can just create a method that returns an IQueryable<Category>. If you want the usage to be the same as your example then this could be an extension method:

public static IQueryable<Category> GetExpression(this IQueryable<Category> qry)

{

    var expression = qry.Include(cat => cat.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.GraphicItems)

                .ThenInclude(itm => itm.Graphic)

                    .ThenInclude(gfx => gfx.Items)

        .Include(cat => cat.GraphicItems)

            .ThenInclude(gfx => gfx.Graphic)

                .ThenInclude(gfx => gfx.Items)

        .Include(m => m.Modules);



    return expression;

}

You can then use this as follows:

await this.Worker

    .GetRepo<Category>()

    .GetExpression()

    .SingleAsync(cat => cat.UId.Equals(uid));

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

1

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

add a comment |

up vote
3
down vote

accepted

You can just create a method that returns an IQueryable<Category>. If you want the usage to be the same as your example then this could be an extension method:

public static IQueryable<Category> GetExpression(this IQueryable<Category> qry)

{

    var expression = qry.Include(cat => cat.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.GraphicItems)

                .ThenInclude(itm => itm.Graphic)

                    .ThenInclude(gfx => gfx.Items)

        .Include(cat => cat.GraphicItems)

            .ThenInclude(gfx => gfx.Graphic)

                .ThenInclude(gfx => gfx.Items)

        .Include(m => m.Modules);



    return expression;

}

You can then use this as follows:

await this.Worker

    .GetRepo<Category>()

    .GetExpression()

    .SingleAsync(cat => cat.UId.Equals(uid));

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

1

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

add a comment |

up vote
3
down vote

accepted

You can just create a method that returns an IQueryable<Category>. If you want the usage to be the same as your example then this could be an extension method:

public static IQueryable<Category> GetExpression(this IQueryable<Category> qry)

{

    var expression = qry.Include(cat => cat.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.GraphicItems)

                .ThenInclude(itm => itm.Graphic)

                    .ThenInclude(gfx => gfx.Items)

        .Include(cat => cat.GraphicItems)

            .ThenInclude(gfx => gfx.Graphic)

                .ThenInclude(gfx => gfx.Items)

        .Include(m => m.Modules);



    return expression;

}

You can then use this as follows:

await this.Worker

    .GetRepo<Category>()

    .GetExpression()

    .SingleAsync(cat => cat.UId.Equals(uid));

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

You can just create a method that returns an IQueryable<Category>. If you want the usage to be the same as your example then this could be an extension method:

public static IQueryable<Category> GetExpression(this IQueryable<Category> qry)

{

    var expression = qry.Include(cat => cat.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.InfoItems)

        .Include(cat => cat.Products)

            .ThenInclude(prd => prd.GraphicItems)

                .ThenInclude(itm => itm.Graphic)

                    .ThenInclude(gfx => gfx.Items)

        .Include(cat => cat.GraphicItems)

            .ThenInclude(gfx => gfx.Graphic)

                .ThenInclude(gfx => gfx.Items)

        .Include(m => m.Modules);



    return expression;

}

You can then use this as follows:

await this.Worker

    .GetRepo<Category>()

    .GetExpression()

    .SingleAsync(cat => cat.UId.Equals(uid));

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

edited Nov 11 at 11:08

answered Nov 19 '17 at 1:18

CalC

4,31831833

answered Nov 19 '17 at 1:18

CalC

4,31831833

answered Nov 19 '17 at 1:18

CalC

4,31831833

1

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

add a comment |

1

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

Great, thank you!
– TheRuler
Nov 19 '17 at 1:22

add a comment |

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