Windows forms App

Question

Im am a begginer in c# and i am using visual studio 2022
i find a problem when i use windows forms using entity famework.
if i use windows forms app (.NET Framework) i find this problem

and when i use windows forms app i find this problem of c# language version

i downloaded entity framework

in both of windows forms app types

i need help please

Answer 1

From the Error that is shown under Error List, can you add this: <LangVersion>latest</LangVersion> under <PropertyGroup> please. Something like below,

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net6.0-windows</TargetFramework>
    <Nullable>enable</Nullable>
    <UseWindowsForms>true</UseWindowsForms>
    <ImplicitUsings>enable</ImplicitUsings>
    <LangVersion>latest</LangVersion>
  </PropertyGroup>

</Project>

Answer 2

@mehdi selk , Based on your picture, I find that you are using .net core winform. Therefore, we need to use EF core to get data from database instead of Entityframework.

Please refer to the following steps to use ef-core in .net core winform app.

First, Please install the following nuget-package: (Please choose other type of ef core If you access other database)

Second, Please create model class and dbcontext class.

public class Student  
{  
    [Key]  
    public int Id { get; set; }   
  
    public string Name { get; set; }          
  
    public DateTime Date { get; set; }  
}  
  
  
public class MyDbContext:DbContext  
{  
    public DbSet<Student> Students { get; set; }  
  
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)  
    {  
        optionsBuilder.UseSqlServer(@"connstr");  
    }  
         
}  

Third, Please execute the following command in your Package Manager Console window.

 Add-Migration First  
  
 Update-Database  

Finally, you could try the following code to insert data to database and show the data in datagridview.

private void Form1_Load(object sender, EventArgs e)  
        {  
            using (MyDbContext dbContext = new MyDbContext())  
            {  
                dbContext.Students.Add(new Student { Id=1001, Date=DateTime.Now, Name="test1" });  
                dbContext.Students.Add(new Student { Id=1002, Date=DateTime.Now, Name="test2" });  
                dbContext.Students.Add(new Student { Id=1003, Date=DateTime.Now, Name="test3" });  
                dbContext.SaveChanges();  
            }  
        }  
        MyDbContext dbContext = new MyDbContext();  
        private void button1_Click(object sender, EventArgs e)  
        {  
            var result = from c in dbContext.Students  
                         select c;  
            dataGridView1.DataSource=result.ToList();  
        }  
  
        private void button2_Click(object sender, EventArgs e)  
        {  
            var result = from c in dbContext.Students  
                         select new  
                         {  
                             c.Name,  
                             c.Date  
                         };  
            dataGridView1.DataSource= result.ToList();  
        }  

Result:

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Answer 3

I have a decent Entity Framework 6 code sample here done a while ago (under windows 7 but will run under windows 10) using SQL-Server. Before using you must open NuGet package manager and perform a restore.