.NET (Core and Framework)

Re: How to know which Id belongs to which object?

1-Apr-20 13:05

You should be able to change the navigation property names in the model browser:
c# - Entity Framework (Database-First) multiple relations to same table naming conventions control - Stack Overflow[^]

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

simpledeveloper2-Apr-20 6:30

An expression tree lambda may not contain a null propagating operator

2-Apr-20 6:30

Thank you Deeming - thanks a lot my friend Smile | :)

simpledeveloper27-Mar-20 21:38

Re: An expression tree lambda may not contain a null propagating operator

27-Mar-20 21:38

I am getting the following error when I am write the following Linq - can somebody please suggest me to write the same without getting the error.
My Linq is as follows:

myOrphanList =
        (
            from v in allViolations
            from r in allInspectionResults
            from i in allItems
            where
                r.InspectionResultId == i.InspectionResultId &&
                i.InspectionItemId == v.InspectionItemId
            select new OrphanViolationsReport
            {
                ViolationId = v.ViolationId,
                ViolationNumber = v.ViolationNumber,
                ViolationDate = v.ViolationDate,
                ViolationType = v.ViolationType.ViolationTypeCode,
                ItemYear = i.ItemYear,
                ItemMakeManufacturer = i.ItemMakeManufacturer,
                ItemModel = i.ItemModel,
                VIN = i.VIN,
                PIN = i.PIN,
                InspectionResultId = r.InspectionResultId,
                InspectionResultNumber = r.InspectionRequestNumber,
                DealerDmvNumber = r.DealerDmvNumber,
                InspectedCompanyName = (from a in contacts where a.ContactId == r.InspectedCompanyDataId select a.FirstName)?.FirstOrDefault()
            }
        ).ToList();

At the line "InspectedCompanyName = (from a in contacts where a.ContactId == r.InspectedCompanyDataId select a.FirstName)?.FirstOrDefault()"
I am getting following error - how can I get rid of it - thank you

An expression tree lambda may not contain a null propagating operator

Any help please

Richard MacCutchan27-Mar-20 23:48

Re: An expression tree lambda may not contain a null propagating operator

27-Mar-20 23:48

It needs an actual value. If you Google the error message you will find a number of suggestions.

Bohdan Stupak28-Mar-20 4:38

Bohdan Stupak

28-Mar-20 4:38

Just ditch question mark in front of FirstOrDefault.

Column length change using Entity Framework Code First

simpledeveloper17-Mar-20 13:59

Re: Column length change using Entity Framework Code First

17-Mar-20 13:59

Hi I am trying to alter a column to fit max length - I changed the entity property and ran Add migration - it did well in the first then in committing it on Git or over written by the remote branch or something its last when I was merging it in master branch then onwards it started giving me issues - my property that I changed is as follows:

[StringLength(7999)]
    public string EventComment { get; set; }

When I am creating - its creating the migration script as below:

public partial class AlterColumnLemgthEventComment : DbMigration
    {
            public override void Up()
            {
            }
            
            public override void Down()
            {
            }
    }

I tried in the following ways to workaround for it
Even though I made it EventComment 1000 in Database then deleted my migration file - then ran the add migration now the file is created in the above way - not able to do anything - now its not let me login to the application as the database is failing - any help please - later its failing if I make the EventComment length max in Database and ran the application - still its failing validation errors. Any help please - just get away from validating any more from Code First, its painful to care things this much. Any help please.

When I make the Database field as Max and Entity property also as 7999 - still it is giving me the following exception in the application - just not able to decide

The field EventComment must be a string with a maximum length of 1000.

I am getting the following error while trying to run the add migration

The Designer Code for this migration file includes a snapshot of your current Code First model. This snapshot is used to calculate the changes to your model when you scaffold the next migration. 
If you make additional changes to your model that you want to include in this migration, then you can re-scaffold it by running 'Add-Migration AlterColumnLemgthEventComment' again.

Any help please?

modified 17-Mar-20 20:27pm.

Gerry Schmitz17-Mar-20 16:22

Gerry Schmitz

17-Mar-20 16:22

Much ado about nothing. Check the length "before" saving instead of relying on "scaffolding".

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Re: Column length change using Entity Framework Code First

simpledeveloper18-Mar-20 3:28

Re: Column length change using Entity Framework Code First

18-Mar-20 3:28

I have to be able to insert max size string rather 1000 length string

Richard Deeming17-Mar-20 23:52

Re: Column length change using Entity Framework Code First

17-Mar-20 23:52

simpledeveloper wrote:
in committing it on Git or over written by the remote branch

If you've got multiple developers generating migrations at the same time, things can get very confused. Especially if you're all using the same development database instance.

Code First Migrations in Team Environments - EF6 | Microsoft Docs[^]

simpledeveloper wrote:
Even though I made it EventComment 1000 in Database then deleted my migration file - then ran the add migration

As explained in the article above, Add-Migration doesn't look at the database; it looks at the model snapshot stored with the last migration. Manually changing the database won't cause EF to generate a migration to change it back.

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

simpledeveloper18-Mar-20 3:14

Re: Column length change using Entity Framework Code First

18-Mar-20 3:14

Can you please help me what can I do now - yes it seems that it is storing in snapshot - how can I clean it up - I am feeling very discomfort in changing things as it stored in snapshot and any mistake like the one above it happened because of merging - it made it very difficult - any help please. Can you please suggest me something please - thank you.

Richard Deeming18-Mar-20 3:55

Resolving the merge conflict - Code First Migrations in Team Environments - EF6 | Microsoft Docs[^]

18-Mar-20 3:55

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

Re: Column length change using Entity Framework Code First

simpledeveloper18-Mar-20 8:43

Re: Column length change using Entity Framework Code First

18-Mar-20 8:43

Hi Richard - how can I freshly generate add migration because its not creating me the same again. So I want to generate the migration file again how can I? The file is gone I am not looking for it - merging links help me but for future to be careful. Now I want to regenerate the migration files with the code what can I do? Its not allowing me. Please need help.

Richard Deeming18-Mar-20 8:48

Re: Column length change using Entity Framework Code First

18-Mar-20 8:48

Read the document I linked to - it explains what you need to do.

Resolving the merge conflict - Code First Migrations in Team Environments - EF6 | Microsoft Docs[^]

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

simpledeveloper19-Mar-20 5:54

c# forms (holy crap i'm not ready for this)

19-Mar-20 5:54

Again thank you Richard my friend - thanks a lot Smile | :)

Uranium-23513-Mar-20 23:51

13-Mar-20 23:51

It was so simple in VB, accessing other forms properties.

The main form, right after it's drawn, I want to check for a .db file and if it dosen't exist, to make visible a form (already defined) to create it the db file. (form already as always-on-top, but not visible).

After a ton of internet research, i'm still where I started. Closest I got gave me a threading error, which I've learned to work around in VB, but this, is just confusing (TechTracker.CreateDB.ActiveForm.Visible = true;)

I like how much c# is to PHP AFA structure, loops, arrays, strings. But this stuff is confusing me

Richard MacCutchan14-Mar-20 1:07

14-Mar-20 1:07

Uranium-235 wrote:
It was so simple in VB, accessing other forms properties.

The same is true in C#. Perhaps you could show your code and explain exactly where the problem lies.

Uranium-23514-Mar-20 4:37

14-Mar-20 4:37

my main.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SQLite;
using System.IO;

namespace TechTracker
{
          
    
    public partial class Main : Form
    {
        public Main()
        {
            InitializeComponent();
        }


        private void Main_Load(object sender, EventArgs e)
        {
            if(!File.Exists(Directory.GetCurrentDirectory() + "\\Tracker.db"))
            {
                //yeah none of these worked
                //((CreateDB)this.Owner).Show();
                //Form CreateDBForm = CreateDB.FindForm();
                //TechTracker.CreateDB.ActiveForm.Visible = true;
                //System.Windows.Forms.Control.Invoke;
                 

            }
        }
    }
}

createDB.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace TechTracker
{
    public partial class CreateDB : Form
    {
        public CreateDB()
        {
            InitializeComponent();
            
        }
    }
}

both were made as windows forms designer. createDB is not visible by default. As you can see, if the file is not there, they choose to create it as an sqlLite (I know I still have to define it in using in createdb) database. createDB is topmost enabled and won't let the main form be accessible when it's up. That logic shouldn't be hard, i've done it with vb before. I'll later get a better method of detecting the database file (store filepath in registry, or local file). Probably even allow switching DB files in a settings dropdown. For now, this just basic code to get some of the basic functionality out of this way.

I learned VB.net from scratch using only google on trial and error. Got fairly good at it too. It's just these individual methods of c# I need to get out of the way

oh and yes, it's me from the previous post. I decided to go with sqllite instead of mysql or transactional HTTP transfer. I'm making this mainly for me for the time being, and I can just use google drive or something to sync the sqllite db file for housecall (on my laptop) or home use

thank you

Dave Kreskowiak14-Mar-20 4:58

Dave Kreskowiak

14-Mar-20 4:58

Forms are nothing but classes. So how do you create an instance of a class? You "new one up".

CreateDB createForm = new CreateDB();
createForm.ShowDialog();     // Or .Show() depending on requirements

This would be the exact same thing you do in VB.NET.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Uranium-23514-Mar-20 5:35

14-Mar-20 5:35

I remember in VB.net I would use something like My.Forms but it's been a while

Dave Kreskowiak14-Mar-20 6:30

Dave Kreskowiak

14-Mar-20 6:30

That is actually a wrapper around exactly what I posted. What you're calling "in VB.NET" is actually just a bunch of classes in a namespace that wrap this kind of functionality to maintain "backward compatibility" with older VB code.

The wrappers and extensions are not in the language itself, but is in a library of classes. Since it's all in a .NET library, you could even use the library in other languages, like C#, but I wouldn't recommend doing that. What the library does is insulate you from learning and knowing all the gritty details of how things should be done and they actually work.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Richard MacCutchan14-Mar-20 6:11

14-Mar-20 6:11

Uranium-235 wrote:
createDB is topmost enabled and won't let the main form be accessible when it's up.

You don't need Topmost, just make it a dialog so it automatically disables the calling form:

CreateDB dbCreator = new CreateDB();
DialogResult rc = dbCreator.ShowDialog();
// check rc for success etc.

Here is a really useful C# tutorial: http://www.charlespetzold.com/dotnet/index.html[^].

Uranium-23514-Mar-20 6:51

14-Mar-20 6:51

Thank you guys. I was googling for over an hour last night (phrasing?). I still have a lot to learn.

Richard MacCutchan14-Mar-20 7:02

14-Mar-20 7:02

You will never learn programming from Google or Youtube. Get yourself a decent book that will teach you properly, starting with the basics. Time spent now will pay dividends in the future.

Uranium-23514-Mar-20 20:42