Question

Using Entity Framework in C#, I get this error:

The entry ‘AlMizanEntities’ has already been added.
(D:\Document\Almizan\AlMizan\C#\AlMizan\bin\Debug\AlMizan.vshost.exe.config
line 7)

My code:

private void Fraz()
{
    label1.Text = "Fraz ...";
    Application.DoEvents();

    AlMizanEntities1 ObjAE = new AlMizanEntities1();
}

public partial class AlMizanEntities1 : ObjectContext
{
   /// <summary>
   /// Initializes a new AlMizanEntities1 object using the connection string found in the 'AlMizanEntities1' section of the application configuration file.
   /// </summary>
   // *ERROR* occurs here
   public AlMizanEntities1() : base("name=AlMizanEntities1", "AlMizanEntities1")
   {
      this.ContextOptions.LazyLoadingEnabled = true;
      OnContextCreated();
   }

   /// <summary>
   /// Initialize a new AlMizanEntities1 object.
   /// </summary>
   public AlMizanEntities1(string connectionString) : base(connectionString, "AlMizanEntities1")
   {
        this.ContextOptions.LazyLoadingEnabled = true;
        OnContextCreated();
   }

   /// <summary>
   /// Initialize a new AlMizanEntities1 object.
   /// </summary>
   public AlMizanEntities1(EntityConnection connection) : base(connection, "AlMizanEntities1")
   {
        this.ContextOptions.LazyLoadingEnabled = true;
        OnContextCreated();
   }
}

Answer 1

remove line 7 in D:\Document\Almizan\AlMizan\C#\AlMizan\App.config
or remove the duplicated line somewhere else in that file.