I need an exampel for a MVVM with foreign key

simsenVejle

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Joined
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Messages
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I have 2 models
CategoryModel
---CategoryId
---CategoryName
---ProjectId (this i foreign key)

ProjectModel
---ProjectId
---ProjectName

Those I don't have problems in making.

But now it gets tricky to me. What to do in the VM and also in the View.

In the View I have a ListView where the columns are
---CategoryId
---CategoryName
---ProjectName

Right now I have made a 4. entry in the Category that says ProjectName (and there I have made a join in the stored procedure to the 2 tables. But I think that is very bad. Because the ProjectName shouldn't be in the Category Model.

I have looked on google for the hole day and can't find a tutorial that shows me, how to join the 2 models in the viewmodel and if that isn't the right way how the to make the ListView.

I'm properbly using the wrong sentence in google search.

I would be glad for any kind of help.

Best regards
Simsen :)
 
Solution
Unfortunately, your basic relational database setup is wrong. You need the following schema:

Category:
Id
Name

Project:
Id
Name

ProjectCategory:
Id
ProjectId
CategoryId

Skydiver

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Unfortunately, your basic relational database setup is wrong. You need the following schema:

Category:
Id
Name

Project:
Id
Name

ProjectCategory:
Id
ProjectId
CategoryId
 
Last edited:
Solution

simsenVejle

Active member
Joined
Feb 14, 2021
Messages
38
Programming Experience
Beginner
Unfortunately, your basic relational database setup is wrong. You need the following schema:

Category:
Id
Name

Project:
Id
Name

ProjectCategory:
Id
ProjectId
CategoryId
Hi,
Thank you for your answer.

Your db layout is that if there is a many to many relationship. That is mine not. I can only have one project to one category.


If that isn't the case I can't see, what to do in the VM.

In the view I want to show CategoryId, CategoryName and ProjectName (not Id).

So if I took your advise I'm confused what to do in the model and most important how to make it so, I can see the 3 entries from Model in the ViewModel?

Best regards
Simsen :)
 

Skydiver

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So if you have 100 projects, you will have exactly 100 categories? If that's the case, then simply layout your records to be:

Project
Id
Name
Category

and be done with it.
 

simsenVejle

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Programming Experience
Beginner
So if you have 100 projects, you will have exactly 100 categories? If that's the case, then simply layout your records to be:

Project
Id
Name
Category

and be done with it.
I can have a number of categories that hasn't any project. And I can have projects that hasn't been assigned to any Category
 

Skydiver

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Okay, so what's wrong the M:N relationship showed in post #3? There's no requirement that M > 1 or N > 1.
 
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