这是表格
用户
UserId
UserName
Password
EmailAddress
还有代码..
public void ChangePassword(int userId, string password){
//code to update the password..
}
这是表格
用户
UserId
UserName
Password
EmailAddress
还有代码..
public void ChangePassword(int userId, string password){
//code to update the password..
}
当前回答
Ladislav的答案更新为使用DbContext(在EF 4.1中引入):
public void ChangePassword(int userId, string password)
{
var user = new User() { Id = userId, Password = password };
using (var db = new MyEfContextName())
{
db.Users.Attach(user);
db.Entry(user).Property(x => x.Password).IsModified = true;
db.SaveChanges();
}
}
其他回答
结合几项建议,我提出如下:
async Task<bool> UpdateDbEntryAsync<T>(T entity, params Expression<Func<T, object>>[] properties) where T : class
{
try
{
var entry = db.Entry(entity);
db.Set<T>().Attach(entity);
foreach (var property in properties)
entry.Property(property).IsModified = true;
await db.SaveChangesAsync();
return true;
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("UpdateDbEntryAsync exception: " + ex.Message);
return false;
}
}
被
UpdateDbEntryAsync(dbc, d => d.Property1);//, d => d.Property2, d => d.Property3, etc. etc.);
或通过
await UpdateDbEntryAsync(dbc, d => d.Property1);
或通过
bool b = UpdateDbEntryAsync(dbc, d => d.Property1).Result;
在寻找这个问题的解决方案时,我在Patrick Desjardins的博客上找到了GONeale的答案:
public int Update(T entity, Expression<Func<T, object>>[] properties)
{
DatabaseContext.Entry(entity).State = EntityState.Unchanged;
foreach (var property in properties)
{
var propertyName = ExpressionHelper.GetExpressionText(property);
DatabaseContext.Entry(entity).Property(propertyName).IsModified = true;
}
return DatabaseContext.SaveChangesWithoutValidation();
}
如你所见,它的第二个参数是a的表达式 函数。这将允许通过在Lambda中指定使用此方法 表示要更新哪个属性。”
...Update(Model, d=>d.Name);
//or
...Update(Model, d=>d.Name, d=>d.SecondProperty, d=>d.AndSoOn);
(这里也给出了一个类似的解决方案:https://stackoverflow.com/a/5749469/2115384)
我目前在自己的代码中使用的方法,扩展到处理类型ExpressionType.Convert的(Linq)表达式。这在我的例子中是必要的,例如Guid和其他对象属性。它们被“包装”在Convert()中,因此没有被System.Web.Mvc.ExpressionHelper.GetExpressionText处理。
public int Update(T entity, Expression<Func<T, object>>[] properties)
{
DbEntityEntry<T> entry = dataContext.Entry(entity);
entry.State = EntityState.Unchanged;
foreach (var property in properties)
{
string propertyName = "";
Expression bodyExpression = property.Body;
if (bodyExpression.NodeType == ExpressionType.Convert && bodyExpression is UnaryExpression)
{
Expression operand = ((UnaryExpression)property.Body).Operand;
propertyName = ((MemberExpression)operand).Member.Name;
}
else
{
propertyName = System.Web.Mvc.ExpressionHelper.GetExpressionText(property);
}
entry.Property(propertyName).IsModified = true;
}
dataContext.Configuration.ValidateOnSaveEnabled = false;
return dataContext.SaveChanges();
}
您可以告诉EF哪些属性必须以这种方式更新:
public void ChangePassword(int userId, string password)
{
var user = new User { Id = userId, Password = password };
using (var context = new ObjectContext(ConnectionString))
{
var users = context.CreateObjectSet<User>();
users.Attach(user);
context.ObjectStateManager.GetObjectStateEntry(user)
.SetModifiedProperty("Password");
context.SaveChanges();
}
}
在EntityFramework Core 2中。x不需要附加:
// get a tracked entity
var entity = context.User.Find(userId);
entity.someProp = someValue;
// other property changes might come here
context.SaveChanges();
尝试在SQL Server和分析它:
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [User] SET [someProp] = @p0
WHERE [UserId] = @p1;
SELECT @@ROWCOUNT;
',N'@p1 int,@p0 bit',@p1=1223424,@p0=1
Find确保已经加载的实体不会触发SELECT,并在需要时自动附加实体(来自文档):
查找具有给定主键值的实体。如果上下文正在跟踪具有给定主键值的实体,则立即返回该实体,而无需向数据库发出请求。否则,将向数据库查询具有给定主键值的实体,如果找到该实体,则将该实体附加到上下文并返回。如果没有找到实体,则返回null。
在实体框架核心中,Attach返回条目,所以你所需要的是:
var user = new User { Id = userId, Password = password };
db.Users.Attach(user).Property(x => x.Password).IsModified = true;
db.SaveChanges();