Save Register in Bank with Entity

Question

Dear colleagues.

I’m developing an application C# Winform with database SqlServer and Entity framework. As I am inexperienced, I have been learning through the Internet. I’m having a hard time understanding and implementing some concepts regarding object orientation regarding database manipulation.

I’ll put down the parts of my system to see if they can help me make this code work. To be more objective, my code until it was working but without the proper relationships between the tables. When I modified it so that the tables had relationships began to give errors, as this following.

I appreciate the help.

System.Data.Entity.Infrastructure.Dbupdateexception Hresult=0x80131501 Message=Entities in 'Bancocontexto.Pedidoctx' participate in the 'Cliente_pedidoprincipalx' Relationship. 0 Related 'Cliente_pedidoprincipalx_source' Were found. 1 'Cliente_pedidoprincipalx_source' is expected.

namespace DAL.MODEL
{
    public class Cliente
    {
        public Cliente()
        {
            this.PedidoPrincipalX = new List<PedidoPrincipal>();
        }

        public int ClienteId { get; set; }
        public string Nome { get; set; }

        public virtual ICollection<PedidoPrincipal> PedidoPrincipalX { get; set; }
    }
}

namespace DAL.MODEL
{
    public class PedidoPrincipal
    {
        public int PedidoId { get; set; }
        public DateTime DataEmissao { get; set; }
        public Decimal Total { get; set; }

        public int FK_ClienteId { get; set; }
        public virtual Cliente ClienteX { get; set; }
    }
}

namespace DAL.MAPPING
{
    public class ClienteMap : EntityTypeConfiguration<Cliente>
    {
        public ClienteMap()
        {
            ToTable("Cliente");
            HasKey(c => c.ClienteId);
            Property(c => c.ClienteId).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
            HasMany(X => X.PedidoPrincipalX);
        }
    }
}


namespace DAL.MAPPING
{
    public class PedidoPrincipalMap : EntityTypeConfiguration<PedidoPrincipal>
    {
        public PedidoPrincipalMap()
        {
            ToTable("PedidoPrincipal");
            HasKey(p => p.PedidoId);
            Property(p => p.PedidoId).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
            HasRequired(X => X.ClienteX);
        }
    }
}

Code snippet to save to bank:

private void btnSalvar_Click(object sender, EventArgs e)
{
    PedidoPrincipalRepositorio app = new PedidoPrincipalRepositorio();

    PedidoPrincipal pedido = new PedidoPrincipal();

    pedido.FK_ClienteId = Int32.Parse(txtCodigoCli.Text);

    pedido.DataEmissao = DateTime.Now;
    pedido.Total = decimal.Parse(txtValorTotal.Text);

    app.Adicionar(pedido);
    app.SalvarTodos();
}

Answer 1

First we will make some changes to your Model, to make your life easier, we will use the conventions of Code First.

namespace DAL.MODEL{

    public class Cliente
    {
        public Cliente()
        {
            this.PedidoPrincipalX = new List<PedidoPrincipal>();
        }

        public int Id { get; set; }
        public string Nome { get; set; }

        public virtual ICollection<PedidoPrincipal> PedidoPrincipalX { get; set;} 
    }
}

Modifications

• Replaces public int ClienteId { get; set; }for public int Id { get; set; }, in this way we use the conversion of EPH, thus he comes to understand that ID is the primary key of the entity Client, and will use that same key as FK, in their relationships

---

namespace DAL.MODEL
{
    public class PedidoPrincipal
    {
        public int Id { get; set; }
        public DateTime DataEmissao { get; set; }
        public Decimal Total { get; set; }
        public int ClienteId {get;set;}

        public virtual Cliente ClienteX { get; set; }
    }
}

Modifications:

• Replaces public int PedidoId { get; set; } by public int Id { get; set; }`, at least from above, to maintain the convention, thus the simple fact of using the virtual properties, will cause the EPH understand the relationship automatically

• I removed public int FK_ClienteId { get; set; }, because we adopt the conventions of EPH, this property becomes unnecessary, and may even hinder the EPH.

• Includes public int ClienteId {get;set;}, replacing the removed property, so you can use it to connect the customer to the order. Note: You must follow the writing pattern, {class name+Id}, so the EF will identify this properties as FK.

---

Well, now that we’ve solved the model, let’s go to Mappings:

namespace DAL.MAPPING{

    public class ClienteMap : EntityTypeConfiguration<Cliente>
    {
        public ClienteMap(){
            Property(c => c.ClienteId)
              .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
        }
    }
}


namespace DAL.MAPPING
{
    public class PedidoPrincipalMap : EntityTypeConfiguration<PedidoPrincipal>{
        public PedidoPrincipalMap()
        {
            Property(p => p.PedidoId)                   
               .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
        }
    }
 }

Modifications:

• We leave only the configuration of HasDatabaseGeneratedOption, as I said above, using the conventions of EPH, all the relationship part is already created automatically, so it becomes unnecessary this setting by Fluent Api.

---

This way your code gets clean, easy to understand, and decrease those chances of relationship mistakes. The link I passed on the conventions also has several tutorials on things you will need, I think a good, will help you a lot in this beginning, was what I used as a source of study to learn.