Entity framework add new entity

Question

I unable to insert a record in table

public class KPITable
{

    [Key]        
    public int Id { get; set; }
    public string Name { get; set; }
    public string Query { get; set; }
    public string TableName { get; set; }
}

public class KPITableMap : EntityTypeConfiguration<KPITable>
{
    public KPITableMap()
    {
        ToTable("EIS_KPI", AppUtility.EISMDBSchemaName);
        Property(t => t.Id).HasColumnName("KPI_ID");           
        Property(t => t.Name).HasColumnName("NAME").HasMaxLength(20);
        Property(t => t.Query).HasColumnName("QUERY").HasMaxLength(20);
        Property(t => t.TableName).HasColumnName("TABLE_NAME").HasMaxLength(20);

    }
}

I am getting error when i try to add new entity

A null store-generated value was returned for a non-nullable member 'Id' of type 'EISM.Database.Models.KPITable

var newEntity = new KPITable();
newEntity.Id = 55;
                newEntity.Name = data.Name;
                newEntity.Query = data.Query;
                newEntity.TableName = data.TableName;
_dbContext.KPIs.Attach(newEntity);
                _dbContext.Entry(newEntity).State = EntityState.Added;
                _dbContext.SaveChanges();

Answer 1

this has resolved my problem

[Key]     
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }

OR you can just remove this line

[DatabaseGenerated(DatabaseGeneratedOption.Computed)]

Answer 2

This should work:

var newEntity = new KPITable();
newEntity.Id = 55;
                newEntity.Name = data.Name;
                newEntity.Query = data.Query;
                newEntity.TableName = data.TableName;
_dbContext.KPIs.AddObject(newEntity);
_dbContext.SaveChanges();

Attach is for existing entities (when they are detached, or when you want to attach it to another entity).

AddObject is for new entities.