C#笔记: 项目通过EF框架操作SQLCE数据库

(转载请注明来源:cnblogs coder-fang) 

1.　　项目添加package:

2.　　创建好sqlce数据库并设计好关系表，在项目中添加ado.net 实体数据模型，并连接到此数据 库。

3.　　如果不想在app.config暴露数据库敏感字段(如密码)时， 在创建实体模型时，进行如下选择:

4.　　修改自动生成的Context.cs：

5.　　在此文件中，增加一个构造函数 :

6.创建sqlcceprovider,填写连接字串:

 public abstract class SqlceProvider
    {
        protected const string DBUtilVersion = "1.0";
        protected EntityConnectionStringBuilder ecb;
        protected EntityConnectionStringBuilder ecbReadOnly;

        public SqlceProvider(string dataSource)
        {
            ecb = new EntityConnectionStringBuilder()
            {
                Metadata = "res://*/DAO.SQLCEStorage.csdl|res://*/DAO.SQLCEStorage.ssdl|res://*/DAO.SQLCEStorage.msl",
                Provider = "System.Data.SqlServerCe.4.0",
                ProviderConnectionString = "Data Source=" + dataSource +";"+
                "Default Lock Timeout=2000;Persist Security Info=false;Max Database Size=4091;Password=123456;"
            };                    
        }
        protected String FindExceptMsg(Exception e)
        {
            return e.InnerException == null ? e.Message : FindExceptMsg(e.InnerException);

        }
    }

7.　　创建子类，并实现业务数据的增删改查:

public partial class SqlceStorageProvider : SqlceProvider, IStorage, IDisposable
    {
        static Object objCreate = new Object();
        Entities db;
        public SqlceStorageProvider(string dataSource = "./Store.db") : base(dataSource)
        {
            db = new Entities(ecb.ConnectionString);

            try
            {
                Config v = db.Config.Find("DBVersion");
                if (!v.value.Equals(DBUtilVersion))
                {
                    throw new Exception("Database version is not compatible");
                }
            }
            catch (DbEntityValidationException e)
            {
                throw new DBException(e.HResult, (e.EntityValidationErrors.Count() > 0) ? e.EntityValidationErrors.First().ValidationErrors.First().ErrorMessage : e.Message);

            }
            catch (Exception e)
            {
                throw new DBException(e.HResult, FindExceptMsg(e));

            }


        }

        public List<Patient> FindPatient(int page, int size, out int total, out DBException err, Patient search = null)
        {
            List<Patient> ret = null;
            total = 0;
            err = new DBException();
            lock (this)
            {
                try
                {

                    var query = from p in db.Patient select p;
                    if (search != null)
                    {
                        if (search.FamilyName != null)
                        {
                            query = query.Where(p => p.FamilyName.StartsWith(search.FamilyName));
                        }
                    }

                    total = query.Count();
                    return query.OrderByDescending(p => p.id).Skip((page - 1) * size).Take(size).ToList();
                }
                catch (DbEntityValidationException e)
                {
                    err.Code = e.HResult;
                    err.Msg = (e.EntityValidationErrors.Count() > 0) ? e.EntityValidationErrors.First().ValidationErrors.First().ErrorMessage : e.Message;
                }
                catch (Exception e)
                {

                    err.Code = e.HResult;
                    err.Msg = FindExceptMsg(e);
                }
                return ret;


            }


        }

        public int SaveOrChangePatient(Patient p, out DBException err)
        {
            int ret = -1;
            err = new DBException();
            lock (this)
            {
                try
                {
                    if (p.id > 0)
                    {
                        db.Entry(p).State = EntityState.Modified;
                    }
                    else
                    {
                        db.Patient.Add(p);
                    }

                    db.SaveChanges();

                    return p.id;
                }
                catch (DbEntityValidationException e)
                {
                    err.Code = e.HResult;
                    err.Msg = (e.EntityValidationErrors.Count() > 0) ? e.EntityValidationErrors.First().ValidationErrors.First().ErrorMessage : e.Message;
                }
                catch (Exception e)
                {
                    err.Code = e.HResult;
                    err.Msg = FindExceptMsg(e);
                }
                return ret;


            }

        }

        public Boolean RemovePatient(Patient p, out DBException err)
        {
            bool ret = false;
            err = new DBException();
            lock (this)
            {

                try
                {
                    db.Entry(p).State = EntityState.Deleted;
                    db.SaveChanges();
                    return true;
                }
                catch (DbEntityValidationException e)
                {
                    err.Code = e.HResult;
                    err.Msg = (e.EntityValidationErrors.Count() > 0) ? e.EntityValidationErrors.First().ValidationErrors.First().ErrorMessage : e.Message;
                }
                catch (Exception e)
                {
                    err.Code = e.HResult;
                    err.Msg = FindExceptMsg(e);
                }
                return ret;

            }

        }
}

8. 级联查询代码示例:

var query = from s in db.Study.Include("Patient") select s;
if (search.Patname != "")
    {
      query = query.Where(s => s.Patient.FamilyName.StartsWith(search.Patname));
    }

9.通过EF实现SQLCE操作已完成，直接创建DB实例，即可对数据库进行操作。