insert data from source to destination with no primary key

Hello Meghana M ,
To define Keyless Entities in EF, there are two ways : based  in your example 
1- Use data annotation [Keyless]. Annotate a model with this attribute

[Keyless]
 public class Data
    {
        public string Abc { get; set; }
        public string cde { get; set; }
        public string efg{ get; set; }
      }

OR

2- use fluent API .HasNoKey to define the keyless entity

// DbContext
public class Data2DBcontext : DbContext
{
    public Data2DBcontext(DbContextOptions<Data2DBcontext> options)
        : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Data>()
            .HasNoKey();
    }

    public DbSet<Data> Datas { get; set; }
}

BENCHAABAN Ali
 

Once you have the data in the destinationData list, you can insert it into the destination table using the AddRange method of the DbContext class.

_dbContext.Data2.AddRange(destinationData);
_dbContext.SaveChanges();

This will insert all the data from the destinationData list into the Data2 table.

To insert data from a source to a destination table in Entity Framework Core with different column names and no primary key, you can use a combination of LINQ and mapping to achieve this. Fetch the data from the source table and map it to the destination table. 

var sourceData = _dbContext.Data.ToList();

var destinationData = sourceData.Select(s => new Data2
{
    A_Abc = s.Abc,
    A_cde = s.cde,
    A_efg = s.efg
}).ToList();

after using fluent API .HasNoKey to define the keyless entity issue is resolved but again getting another error invalid column name

source table

column name : abc,bcd,egf

destination table:

column name: A_abc,A_bcd,A_egf