C# 将两个方法合并为一个泛型方法
我的DAL中有两个相同的方法,它们基于作为参数提供的主键返回数据库行。数据库上下文是linqtoSQL。一个传入字符串参数,第二个传入int参数。我认为必须使用泛型来创建一个接受string或int但不确定如何接受的方法C# 将两个方法合并为一个泛型方法,c#,linq-to-sql,C#,Linq To Sql,我的DAL中有两个相同的方法,它们基于作为参数提供的主键返回数据库行。数据库上下文是linqtoSQL。一个传入字符串参数,第二个传入int参数。我认为必须使用泛型来创建一个接受string或int但不确定如何接受的方法 /// <summary> /// Select table row by integer Primary Key Value /// </summary> /// <typeparam name="T">&l
/// <summary>
/// Select table row by integer Primary Key Value
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="id">The PK value to search for</param>
/// <returns>Single matching PK to id</returns>
public T SelectRowByPk<T>(int id) where T : class
{
using (var dc = new DBDataContext())
{
// Get the table by the type passed in
var table = dc.GetTable<T>();
// Get the metamodel mappings (database to domain objects)
MetaModel modelMap = table.Context.Mapping;
// Get the data members for this type
ReadOnlyCollection<MetaDataMember> dataMembers =
modelMap.GetMetaType(typeof (T)).DataMembers;
// Find the primary key field name by checking for IsPrimaryKey
string pk = (dataMembers.Single(m => m.IsPrimaryKey)).Name;
// Return a single object where the id argument matches the primary key
field value
return table.SingleOrDefault(delegate(T t)
{
int memberId =
Convert.ToInt16(t.GetType().GetProperty(pk).GetValue(t, null));
return memberId == id;
});
}
}
/// <summary>
/// Select table row by Varchar Primary Key Value
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="id">The PK value to search for</param>
/// <returns>Single matching PK to id</returns>
public T SelectRowByVarcharPk<T>(string id) where T : class
{
using (var dc = new DBDataContext())
{
// Get the table by the type passed in
var table = dc.GetTable<T>();
// Get the metamodel mappings (database to domain objects)
MetaModel modelMap = table.Context.Mapping;
// Get the data members for this type
ReadOnlyCollection<MetaDataMember> dataMembers =
modelMap.GetMetaType(typeof(T)).DataMembers;
// Find the primary key field name by checking for IsPrimaryKey
string pk = (dataMembers.Single(m => m.IsPrimaryKey)).Name;
// Return a single object where the id argument matches the primary key
field value
return table.SingleOrDefault(delegate(T t)
{
string memberId =
t.GetType().GetProperty(pk).GetValue(t, null).ToString();
return memberId == id;
});
}
}
指定类型参数的要点之一是,这样就可以拥有动态参数类型。在本例中,“id”将成为您指定的任何类型。您不能直接使用泛型将两个方法合并为一个,但是您可以结合泛型使用一点重构来获得干净的设计: 创建一个私有方法,使用两个通用参数执行繁重的工作,一个用于实体类型,另一个用于主键类型:
private T SelectRowById<T, TId>(TId id) where T : class
{
using (var dc = new DBDataContext())
{
// Get the table by the type passed in
var table = dc.GetTable<T>();
// Get the metamodel mappings (database to domain objects)
MetaModel modelMap = table.Context.Mapping;
// Get the data members for this type
ReadOnlyCollection<MetaDataMember> dataMembers =
modelMap.GetMetaType(typeof(T)).DataMembers;
// Find the primary key field name by checking for IsPrimaryKey
string pk = (dataMembers.Single(m => m.IsPrimaryKey)).Name;
// Return a single object where the id argument matches the primary key
field value
return table.SingleOrDefault(delegate(T t)
{
var memberId =
(TId)t.GetType().GetProperty(pk).GetValue(t, null);
return memberId == id;
});
}
}
在此之后,可以为使用此私有方法的特定id类型声明两个公共方法:
public T SelectRowById<T>(string id) where T : class
{
return SelectRowById<T, string>(id);
}
public T SelectRowById<T>(int id) where T : class
{
return SelectRowById<T, int>(id);
}
通过这种方式,您将拥有一个干净的公共界面,代码重复最少
public T SelectRowById<T>(string id) where T : class
{
return SelectRowById<T, string>(id);
}
public T SelectRowById<T>(int id) where T : class
{
return SelectRowById<T, int>(id);
}