Use string instead of entity class

Question

I am working in Windows forms application (using Entity Framework) and I have several tables in my database. These tables are similar (they have the same quantity of columns with the same column names), except that they (tables) have different names (it means, I have several entity classes).

On the firstForm (MainForm) I have a listbox, which contains all the table names I have. when the user selects one of them, the new form opens (addForm). On this form I have several textboxes to fill the table with data.

My problem is that I want to add data to the tables with universal method using Entity Framework. In general, if I have table called Customer with customerName and customerAge columns (and it corresponding class with the same name) I add data to it like this:

using(var context = new MyDbContext())
{
     var newCustomer = new Customer {customerName = "Alex", customerAge = "24"};
     context.Customers.Add(newCustomer);
     context.SaveChanges();
}

I don't want to write the code for every table in my database. I think that, when the item will be selected in the listbox, I have to pass the specific class name to constructor and then transform this name (type of string) into the specific class to add data to the specific table associated with this name.

How I can do this?

Another example - Supplier table:

using(var context = new MyDbContext())
{
     var newSupplier = new Customer { supplierName = "Bob", supplierAge =  "20" };
     context.Suppliers.Add(newSupplier);
     context.SaveChanges();
}

Answer 1

If the logic is the same for all items, you could just make use of generics and do something like this:

public class Writer<T> where T:class
{
    private DbContext _context;
    public Writer(DbContext context)
    {
        _context = context;
    }

    public void Insert(T obj)
    {
        _context.Set<T>().Add(obj);
        _context.SaveChanges();
    }
}

You have to provide it with your EF context and specify which type you wish to use.

Hope this helps at least point you in the right direction.

Answer 2

You can use reflection to accomplish this task:

Entity classes and context class:

public class Person1
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Person2
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
}

public class MyContext : DbContext
{
    public MyContext() : base ("connection string") { }

    public DbSet<Person1> Person1 { get; set; }
    public DbSet<Person2> Person2 { get; set; }
}

Example program, which having database name can add given entity to it using reflection:

//I guess you can take this values from controls on your form
string database = "Person1";
int id = 1;
string name = "Charlie";
//get type of an entity
Type entityType = this.GetType().Assembly.GetTypes().Where(t => t.Name == database).First();
//geet object of an entity class
var entity = Activator.CreateInstance(entityType);
//set properties (name and id)
entity.GetType().GetProperty("Id").SetValue(entity, id);
entity.GetType().GetProperty("Name").SetValue(entity, name);
MyContext ctx = null;
try
{
    ctx = (MyContext)Activator.CreateInstance(typeof(MyContext));
    //here we'll loop thorugh properties of context (through databases),
    //if name match, add entity using reflection
    foreach (PropertyInfo property in ctx.GetType().GetProperties())
    {
        if (property.Name == database)
        {
            var dbSet = property.GetValue(ctx);
            //get Add method and invoke it with entity object
            dbSet.GetType().GetMethod("Add").Invoke(dbSet, new object[]{ entity });
            ctx.SaveChanges();
        }
    }
}
finally
{
    //always remeber to call Dispose method!
    if(ctx != null)
        ctx.Dispose();
}

Answer 3

You can use DbContext.Database.ExecuteSqlCommand method:

public class Customer : Entity
{
}

public class Supplier : Entity
{
}

public void CreateEntity(string TableName, Entity entity)
{
    using(var context = new MyDbContext())
    {
        var name = new SqlParameter("@name", entity.customerName);
        var age = new SqlParameter("@age", entity.customerAge); 

        context.Database.ExecuteSqlCommand($"insert into {TableName} (customerName, customerAge) values (@name, @age)", 
             name, age);
    }
}