LINQ Getting Started Problem

Question

I am trying to build my hello-world program in LINQ.

While executing the following code:

(This is my LINQ to SQL class which is generated by VS2008.)

#pragma warning disable 1591
//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     Runtime Version:2.0.50727.3053
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

namespace LINQ_to_SQL_Test
{
    using System.Data.Linq;
    using System.Data.Linq.Mapping;
    using System.Data;
    using System.Collections.Generic;
    using System.Reflection;
    using System.Linq;
    using System.Linq.Expressions;
    using System.ComponentModel;
    using System;


    [System.Data.Linq.Mapping.DatabaseAttribute(Name="LINQ_Test")]
    public partial class PersonDataContext : System.Data.Linq.DataContext
    {

     private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();

    #region Extensibility Method Definitions
    partial void OnCreated();
    partial void InsertPerson(Person instance);
    partial void UpdatePerson(Person instance);
    partial void DeletePerson(Person instance);
    #endregion

     public PersonDataContext() : 
       base(global::LINQ_to_SQL_Test.Properties.Settings.Default.LINQ_TestConnectionString, mappingSource)
     {
      OnCreated();
     }

     public PersonDataContext(string connection) : 
       base(connection, mappingSource)
     {
      OnCreated();
     }

     public PersonDataContext(System.Data.IDbConnection connection) : 
       base(connection, mappingSource)
     {
      OnCreated();
     }

     public PersonDataContext(string connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
       base(connection, mappingSource)
     {
      OnCreated();
     }

     public PersonDataContext(System.Data.IDbConnection connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
       base(connection, mappingSource)
     {
      OnCreated();
     }

     public System.Data.Linq.Table<Person> Persons
     {
      get
      {
       return this.GetTable<Person>();
      }
     }
    }

    [Table(Name="dbo.Person")]
    public partial class Person : INotifyPropertyChanging, INotifyPropertyChanged
    {

     private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);

     private int _ID;

     private System.Nullable<int> _IDRole;

     private string _LastName;

     private string _FirstName;

    #region Extensibility Method Definitions
    partial void OnLoaded();
    partial void OnValidate(System.Data.Linq.ChangeAction action);
    partial void OnCreated();
    partial void OnIDChanging(int value);
    partial void OnIDChanged();
    partial void OnIDRoleChanging(System.Nullable<int> value);
    partial void OnIDRoleChanged();
    partial void OnLastNameChanging(string value);
    partial void OnLastNameChanged();
    partial void OnFirstNameChanging(string value);
    partial void OnFirstNameChanged();
    #endregion

     public Person()
     {
      OnCreated();
     }

     [Column(Storage="_ID", DbType="Int NOT NULL", IsPrimaryKey=true)]
     public int ID
     {
      get
      {
       return this._ID;
      }
      set
      {
       if ((this._ID != value))
       {
        this.OnIDChanging(value);
        this.SendPropertyChanging();
        this._ID = value;
        this.SendPropertyChanged("ID");
        this.OnIDChanged();
       }
      }
     }

     [Column(Storage="_IDRole", DbType="Int")]
     public System.Nullable<int> IDRole
     {
      get
      {
       return this._IDRole;
      }
      set
      {
       if ((this._IDRole != value))
       {
        this.OnIDRoleChanging(value);
        this.SendPropertyChanging();
        this._IDRole = value;
        this.SendPropertyChanged("IDRole");
        this.OnIDRoleChanged();
       }
      }
     }

     [Column(Storage="_LastName", DbType="VarChar(50)")]
     public string LastName
     {
      get
      {
       return this._LastName;
      }
      set
      {
       if ((this._LastName != value))
       {
        this.OnLastNameChanging(value);
        this.SendPropertyChanging();
        this._LastName = value;
        this.SendPropertyChanged("LastName");
        this.OnLastNameChanged();
       }
      }
     }

     [Column(Storage="_FirstName", DbType="VarChar(50)")]
     public string FirstName
     {
      get
      {
       return this._FirstName;
      }
      set
      {
       if ((this._FirstName != value))
       {
        this.OnFirstNameChanging(value);
        this.SendPropertyChanging();
        this._FirstName = value;
        this.SendPropertyChanged("FirstName");
        this.OnFirstNameChanged();
       }
      }
     }

     public event PropertyChangingEventHandler PropertyChanging;

     public event PropertyChangedEventHandler PropertyChanged;

     protected virtual void SendPropertyChanging()
     {
      if ((this.PropertyChanging != null))
      {
       this.PropertyChanging(this, emptyChangingEventArgs);
      }
     }

     protected virtual void SendPropertyChanged(String propertyName)
     {
      if ((this.PropertyChanged != null))
      {
       this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
      }
     }
    }
}
#pragma warning restore 1591

This is my hand-coded driver program:

class Program
    {
        static void Main(string[] args)
        {
            PersonDataContext dc = new PersonDataContext("LINQ_TestConnectionString");

            Person person = new Person();
            person.ID = 4;
            person.IDRole = 1;
            person.FirstName = "aaa";
            person.LastName = "bbb";

            dc.Persons.InsertOnSubmit(person);
            dc.SubmitChanges();
        }
    }

I am getting the following error message from SQL Server.

A network-related or instance-specific error occurred while 
establishing a connection to SQL Server. The server was not found 
or was not accessible. Verify that the instance name is correct 
and that SQL Server is configured to allow remote connections. 
(provider: Named Pipes Provider, error: 40 - Could not open a 
connection to SQL Server)

How can I solve the problem?

Answer 1

You're passing the string literal "LINQ_TestConnectionString" into the constructor - so it's treating that as the connection string itself. That's not the connection string, it's just the name of the connection string setting.

The the parameterless constructor - that will automatically use the LINQ_TestConnectionString setting:

PersonDataContext dc = new PersonDataContext();

Alternatively, pass in a real connection string.

Answer 2

Since you draged and dropped the table from the database the connection string is already there just use the default constractor :

new PersonDataContext();

if you want to pass a connection string use this :

Data Source=ComputerName\Instancename;Initial Catalog=DataBaseName;Persist Security Info=True;