Question

我正在尝试在LINQ中构建我的hello-world程序。

执行以下代码时：

（这是我的VSQ8生成的LINQ to SQL类。）

#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

这是我的手动编码驱动程序：

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();
        }
    }

我从SQL Server收到以下错误消息。

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)

我该如何解决这个问题？

Answer 1

您将字符串文字"LINQ_TestConnectionString"传递给构造函数 - 因此它将其视为连接字符串本身。这不是连接字符串，它只是连接字符串设置的名称。

无参数构造函数 - 将自动使用LINQ_TestConnectionString设置：

PersonDataContext dc = new PersonDataContext();

或者，传入真正的连接字符串。

Answer 2

由于您从数据库中删除并删除了表，连接字符串已经存在，只需使用默认约束器：

new PersonDataContext();

如果要传递连接字符串，请使用：

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

LINQ入门问题

2 个答案: