how I can update a single value for an already existing row in the db by only having a parameters that I want to add it to this attribute
here is my code for a trivial way but didnt work
public bool BuyBook(int BookId, int UserId, int BookPrice){
using (var ctx = new OnlineBooksEntities())
{
User updatedCustomer = (from c in ctx.Users
where c.UserId == UserId
select c).FirstOrDefault();
updatedCustomer.Balance = BookPrice;
ctx.SaveChanges();
}
this.DeleteBook(BookId);
return true;
}
Add an sql query to the method solves the update aim
public bool BuyBook(int BookId, int UserId, int BookPrice)
{
try
{
using (var ctx = new OnlineBooksEntities())
{
User user = ctx.Users.Where(x => x.UserId == UserId).FirstOrDefault();
BookPrice = (int)user.Balance + BookPrice;
int noOfRowUpdated =
ctx.Database.ExecuteSqlCommand("Update Users set Balance = "+BookPrice+ " where UserId ="+UserId);
}
Updating basically means changing an existing row's value. Since you mentioned EF, you can do this by retrieving the object, changing its value, and saving it back. Thus you can do something like this:
using (var db = new MyContextDB())
{
var result = db.Books.SingleOrDefault(b => b.BookPrice == bookPrice);
if (result != null)
{
result.SomeValue = "Your new value here";
db.SaveChanges();
}
}
Related
How to save mixed data in multiple tables if is checked checkbox:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "rID,AgentID,karta_br,Datum,patnikID,stanicaOD,stanicaDO,cena,povratna")] tbl_rezervacii tbl_rezervacii)
{
if (ModelState.IsValid)
{
if (tbl_rezervacii.povratna != true)
{
db.tbl_rezervacii.Add(tbl_rezervacii);
db.SaveChanges();
}
else
{
tbl_rezervacii rezervacii = new tbl_rezervacii()
{
???????????????????????
};
db.tbl_rezervacii.Add(rezervacii);
db.SaveChanges();
tbl_povratni povratni = new tbl_povratni()
{
???????????????????????
};
db.tbl_povratni.Add(povratni);
db.SaveChanges();
}
This is code in the controller, and I need to mix data from two forms, and save to two tables, I need something like this, and now my problem is just in else section of implementation.
I make application for Bus Ticket system, and i need this if is checked return way checkbox to add: rID (related with first table tbl_rezervacii), date of returning and relation of returning, include same agent id, price, etc. data which is saved in first tbl_rezervacii table.
MODIFIED CONTROLLER CODE:
public ActionResult Create([Bind(Include = "rID,AgentID,karta_br,Datum,patnikID,stanicaOD,stanicaDO,cena,povratna")] tbl_rezervacii tbl_rezervacii )
{
if (ModelState.IsValid)
{
if (tbl_rezervacii.povratna != true)
{
db.tbl_rezervacii.Add(tbl_rezervacii);
db.SaveChanges();
}
else
{
tbl_rezervacii rezervacii = new tbl_rezervacii()
{
AgentID = tbl_rezervacii.AgentID,
karta_br = tbl_rezervacii.karta_br,
Datum = tbl_rezervacii.Datum,
patnikID = tbl_rezervacii.patnikID,
stanicaOD = tbl_rezervacii.stanicaOD,
stanicaDO = tbl_rezervacii.stanicaDO,
cena = tbl_rezervacii.cena,
povratna = tbl_rezervacii.povratna
};
db.tbl_rezervacii.Add(rezervacii);
//db.SaveChanges();
var rows = db.SaveChanges();
tbl_povratni povratna = new tbl_povratni()
{
rezID = rezervacii.rID,
AgentID = rezervacii.AgentID,
karta_br = rezervacii.karta_br,
DatumP = **tbl_povratni.DatumP**,
patnikID = rezervacii.patnikID,
stanicaPOD = **tbl_povratni.stanicaPOD**,
stanicaPDO = **tbl_povratni.stanicaPDO**,
};
db.tbl_povratni.Add(povratna);
db.SaveChanges();
}
ViewBag.AgentID = new SelectList(db.tbl_agenti, "aID", "agent_ime", tbl_rezervacii.AgentID);
ViewBag.patnikID = new SelectList(db.tbl_patnici, "pID", "ime", tbl_rezervacii.patnikID);
ViewBag.stanicaOD = new SelectList(db.tbl_stanici, "sID", "stanica", tbl_rezervacii.stanicaOD);
ViewBag.stanicaDO = new SelectList(db.tbl_stanici, "sID", "stanica", tbl_rezervacii.stanicaDO);
ViewBag.stanicaPOD = new SelectList(db.tbl_stanici, "sID", "stanica", tbl_rezervacii.tbl_povratni.stanicaPOD);
ViewBag.stanicaPDO = new SelectList(db.tbl_stanici, "sID", "stanica", tbl_rezervacii.tbl_povratni.stanicaPDO);
return View(tbl_rezervacii);
}
return RedirectToAction("Index");
}
How to take data from secondary form and save together in second table?
So, if checkbox is checked, you want to save data into two tables and use primary key of first table (rID) in second table? If rID is auto increment, It will be updated by EF with the value assigned by the database.
tbl_rezervacii rezervacii = new tbl_rezervacii()
{
AgentID = tbl_rezervacii.AgendID,
karta_br = tbl_rezervacii.karta_br
// and so on...
};
db.tbl_rezervacii.Add(rezervacii);
var rows = db.SaveChanges(); // optional, rows will be > 0 if saved successfully.
tbl_povratni povratni = new tbl_povratni()
{
// if rID is auto increment
rID = rezervacii.rID,
// and so on...
};
db.tbl_povratni.Add(povratni);
db.SaveChanges();
I'm trying to get contact details of a contact that the user picks from the contacts list in Android using Intent as the following code:
Intent Intent = new Intent(Intent.ActionPick, ContactsContract.Contacts.ContentUri);
Intent.SetType(ContactsContract.Contacts.ContentType);
StartActivityForResult(Intent, 3);
Now on the Intent results I run the following code to get specific contact information:
public override void OnActivityResult(int requestCode, int resultCode, Intent data)
{
if (requestCode == 3 && resultCode == -1 && data != null) //result code -1 means OK 0 Means cancelled Result.Ok
{
var ContactData = data.Data;
string ID = "";
string name = "";
string address = "";
byte[] picture = new byte[0];
List<string> numbers = new List<string>();
List<string> emails = new List<string>();
string mobile = "";
string email = "";
string selectionString = "id = ?";
string[] columnsNames = new string[] {
ContactsContract.Contacts.InterfaceConsts.Id,
ContactsContract.Contacts.InterfaceConsts.DisplayName,
ContactsContract.Contacts.InterfaceConsts.PhotoUri
};
var loader = new CursorLoader(Statics.mainActivity, ContactData, null, null, null, null);
var cursor = (ICursor)loader.LoadInBackground();
if (cursor.MoveToFirst())
{
ID = cursor.GetString(cursor.GetColumnIndex(columnsNames[0]));
name = cursor.GetString(cursor.GetColumnIndex(columnsNames[1]));
picture = cursor.GetBlob(cursor.GetColumnIndex(columnsNames[2]));
}
//Store Contact ID
string[] selectionStringArgs = new string[] { ID };
//Phone Numbers
string[] columnsNames2 = new string[] {
ContactsContract.CommonDataKinds.Phone.Number
};
var loader2 = new CursorLoader(Statics.mainActivity, ContactsContract.CommonDataKinds.Phone.ContentUri, columnsNames2, selectionString, selectionStringArgs, null);
var cursor2 = (ICursor)loader2.LoadInBackground();
while (cursor2.MoveToNext())
{
numbers.Add(cursor2.GetString(cursor2.GetColumnIndex(columnsNames2[0])));
}
//Email Address
string[] columnsNames3 = new string[] {
ContactsContract.CommonDataKinds.Email.Address
};
var loader3 = new CursorLoader(Statics.mainActivity, ContactsContract.CommonDataKinds.Email.ContentUri, columnsNames3, selectionString, selectionStringArgs, null);
var cursor3 = (ICursor)loader3.LoadInBackground();
while (cursor3.MoveToNext())
{
emails.Add(cursor3.GetString(cursor3.GetColumnIndex(columnsNames3[0])));
}
int TempRecepitntID = 0;
EmployeesViewModel tempRecipent = new EmployeesViewModel();
TempRecepitntID = Statics.mainActivity.currentViewModel.SelectedChat.ReceiverEmployee;
foreach (EmployeesViewModel evm in Statics.mainActivity.currentViewModel.Employees)
{
if (evm.ID == TempRecepitntID)
tempRecipent = evm;
}
new Android.Support.V7.App.AlertDialog.Builder(Statics.mainActivity)
.SetPositiveButton("Yes", (sender1, args) =>
{
Statics.mainActivity.currentViewModel.AddMessage(picture, tempRecipent, Statics.mainActivity.currentViewModel.SelectedChat.ID, "contact", 0, "", name, numbers[0], mobile, email, address);
})
.SetNegativeButton("No", (sender1, args) =>
{
// cancel
})
.SetMessage("Are you shure you want to send?")
.SetTitle("System Message")
.Show();
}
}
The problem is I want to retrieve only the information of the contact that the user selected but what I get is all other contacts data is retrieved so I tried to use the selection and selectionargs parameters of CursorLoader by setting string selectionString = "id = ?"; and selectionArgs to string[] selectionStringArgs = new string[] { ID }; the ID value is retrieved from the following code :
if (cursor.MoveToFirst())
{
ID = cursor.GetString(cursor.GetColumnIndex(columnsNames[0]));
name = cursor.GetString(cursor.GetColumnIndex(columnsNames[1]));
picture = cursor.GetBlob(cursor.GetColumnIndex(columnsNames[2]));
}
//Store Contact ID
string[] selectionStringArgs = new string[] { ID };
//Phone Numbers
string[] columnsNames2 = new string[] {
ContactsContract.CommonDataKinds.Phone.Number
};
But now it returns 0 results, I couldn't find anything on the internet that applies to Xamarin android, Please help.
Thanks,
Finally I found the solution, I used the following string in the selection parameter of the cursorloader method:
string selectionString = ContactsContract.CommonDataKinds.Phone.InterfaceConsts.ContactId + "=" + ID;
and now only the selected contact numbers are retrieved.
I hope this will help someone else.
In additional information of #TMSL, I add the code afer this bloque
if (cursor.MoveToFirst())
{
ID = cursor.GetString(cursor.GetColumnIndex(columnsNames[0]));
name = cursor.GetString(cursor.GetColumnIndex(columnsNames[1]));
picture = cursor.GetBlob(cursor.GetColumnIndex(columnsNames[2]));
}
Here
selectionString = ContactsContract.CommonDataKinds.Phone.InterfaceConsts.ContactId + "=" + ID;
Then I changed the parameters used in the definition of variable Loader2, converting selectionStringArgs in null.
var loader2 = new CursorLoader(this.Activity, ContactsContract.CommonDataKinds.Phone.ContentUri, columnsNames2, selectionString, null,null);
var cursor2 = (ICursor)loader2.LoadInBackground();
I found this documentation from xamarin guides
Uri – The fully qualified name of the ContentProvider.
Projection – Specification of which columns to select for the cursor.
Selection – Similar to a SQL WHERE clause.
SelectionArgs – Parameters to be substituted in the Selection.
SortOrder – Columns to sort by.
So, the variable selectionStringArgs used in the code from #TMSAL cannot use a value like "contact_id = 2700", because the parameter of CursorLoader SelectionArgs is not a filter but not "Parameters to be substituted in the Selection"
I hope this will help someone else too.
I'm refactoring some previously written MVC and Entity Framework code. The way the initial code was written they called a DAL.GetGroupDetail(int groupId) method. In that method it created a ViewModel and populated several properties. Some of those properties are Lists for things like CostCenters, Cities, Groups. I want to break those calls out into their own methods so that they can be re-used in other controllers.
My question is that doing that I'm creating new Contexts using the Using statement. My understanding is that would create multiple connections to the database and thus would slow down the site if multiple users were using it at the same time?
Example, currently this is the basic code:
public ClockGroupViewModel GetClockGroupDetail(int groupId)
{
GroupViewModel cgdv = new GroupViewModel();
using (var ctx = new VTContext())
{
bio_group group = ctx.bio_group.Where(x => x.group_id == groupId).FirstOrDefault();
cgdv.GroupId = group.group_id;
cgdv.GroupName = group.group_name;
cgdv.Cities = ctx.bio_city.ToList();
var clocks = from c in ctx.bio_clock.Where(x => x.group_id == groupId)
select new ClockViewModel
{
ClockID = c.rdr_id.ToString(),
ClockDescription = c.clock_desc,
};
cgdv.ClockList = clocks.ToList();
cgdv.CostCtrList = (from g in ctx.bio_clock_group
from cgc in ctx.bio_clock_group_costctr
where cgc.group_id == g.group_id && g.group_id == groupId
select cgc.cost_ctr).ToList();
}
This how I'm thinking of changing it:
public ClockGroupViewModel GetClockGroupDetail(int groupId)
{
GroupViewModel cgdv = new GroupViewModel();
using (var ctx = new VTContext())
{
bio_group group = ctx.bio_group.Where(x => x.group_id == groupId).FirstOrDefault();
cgdv.GroupId = group.group_id;
cgdv.GroupName = group.group_name;
cgdv.Cities = GetCityList();
cgdv.ClockList = GetClockGroupClockList(group.group_id);
cgdv.CostCtrList = GetGroupCostCenter(group.group_id);
}
}
public List<bio_clock_city> GetCityList()
{
using (var ctx = new VTContext())
{
return ctx.bio_city.ToList();
}
}
public List<ClockViewModel> GetClockGroupClockList(int groupId)
{
using (var ctx = new VTContext())
{
var data = (from c in ctx.bio_clock.Where(x => x.group_id == groupId)
select new ClockViewModel
{
ClockID = c.rdr_id.ToString(),
ClockDescription = c.clock_desc,
}).ToList();
return data;
}
}
public List<string> GetGroupCostCenter(int groupId)
{
using (var ctx = new VTContext())
{
var data = (from g in ctx.bio_clock_group
from cgc in ctx.bio_clock_group_costctr
where cgc.group_id == g.group_id && g.group_id == groupId
select cgc.cost_ctr).ToList();
return data;
}
}
I Create A News Site With MVC5 But I Have Problem .
in Model i Create A Repository Folder And in this i Create Rep_Setting for
Connect to Tbl_Setting in DataBase .
public class Rep_Setting
{
DataBase db = new DataBase();
public Tbl_Setting Tools()
{
try
{
var qGetSetting = (from a in db.Tbl_Setting
select a).FirstOrDefault();
return qGetSetting;
}
catch (Exception)
{
return null;
}
}
}
And i Create a Rep_News for Main Page .
DataBase db = new DataBase();
Rep_Setting RSetting = new Rep_Setting();
public List<Tbl_News> GetNews()
{
try
{
List<Tbl_News> qGetNews = (from a in db.Tbl_News
where a.Type.Equals("News")
select a).OrderByDescending(s => s.ID).Skip(0).Take(RSetting.Tools().CountNewsInPage).ToList();
return qGetNews;
}
catch (Exception ex)
{
return null;
}
}
But This Code Have Error to Me
OrderByDescending(s=>s.ID).Skip(0).Take(RSetting.Tools().CountNewsInPage).ToList();
Error :
Error 18 'System.Linq.IQueryable<NewsSite.Models.Domain.Tbl_News>' does
not contain a definition for 'Take' and the best extension method overload
'System.Linq.Queryable.Take<TSource>(System.Linq.IQueryable<TSource>, int)' has
some invalid arguments
E:\MyProject\NewsSite\NewsSite\Models\Repository\Rep_News.cs 50 52 NewsSite
How i Resolve it ?
Try it this way. The plan of debugging is to split your execution, this also makes for a more reusable method in many cases. And a good idea is to avoid using null and nullables if you can, if you use them "on purpose" the you must have a plan for them.
DataBase db = new DataBase();
Rep_Setting RSetting = new Rep_Setting();
public List<Tbl_News> GetNews()
{
int skip = 0;
Tbl_Setting tools = RSetting.Tools();
if(tools == null){ throw new Exception("Found no rows in the database table Tbl_Setting"); }
int? take = tools.CountNewsInPage;//Nullable
if(!take.HasValue)
{
// Do you want to do something if its null maybe set it to 0 and not null
take = 0;
}
string typeStr = "News";
List<Tbl_News> qGetNews = (from a in db.Tbl_News
where a.Type.Equals(typeStr)
select a).OrderByDescending(s => s.ID).Skip(skip).Take(take.Value);
return qGetNews.ToList();
}
if qGetNews is a empty list you now don't break everything after trying to iterate on it, like your return null would. instead if returning null for a lit return a new List<>() instead, gives you a more resilient result.
So I said reusable method, its more like a single action. So you work it around to this. Now you have something really reusable.
public List<Tbl_News> GetNews(string typeStr, int take, int skip = 0)
{
List<Tbl_News> qGetNews = (from a in db.Tbl_News
where a.Type.Equals(typeStr)
select a).OrderByDescending(s => s.ID).Skip(skip).Take(take);
return qGetNews.ToList();
}
Infact you shjould always try to avoid returning null if you can.
public class Rep_Setting
{
DataBase db = new DataBase();
public Tbl_Setting Tools()
{
var qGetSetting = (from a in db.Tbl_Setting
select a).FirstOrDefault();
if(qGetSetting == null){ throw new Exception("Found no rows in the database table Tbl_Setting"); }
return qGetSetting;
}
}
I want to create a method which can takes the properties I possibly may update and leaving those not interested untouched.
Here is what I did:
public static void updateTable(int id, string field1, string field2, string field3){
using(var context = new Entities()){
var obj = context.Table.Where(x=>x.id == id).FirstOrDefault();
if(obj != null){
obj.field1 = field1;
...
obj.SaveChanges();
}
}
}
But in this pattern, I need to pass all 4 parameters into the method even I just want to update only one field. Is there any generic solution to update only the fields I passed in?
I came up something like this:
public static void updateTable(int id, object data_json){
using(var context = new Entities()){
var obj = context.Table.Where(x=>x.id == id).FirstOrDefault();
if(obj != null){
if(data_json['field1']!=null) //something like this
obj.field1 = data_json['field1'];
...
obj.SaveChanges();
}
}
}
But this can't handle the case that I do want to set a field to be null. Or is there any better solution?
If you don't care about updating relationships, you can use ApplyCurrentValues, which only updates the scalar properties.
E.g:
public static void updateTable(int id, object data_json){
using(var context = new Entities()) {
var obj = context.Table.Where(x=>x.id == id).FirstOrDefault();
context.ApplyCurrentValues("Table", data_json);
}
}
It assumes an entity with the same key is already attached in the graph. In this case, the query for var obj will ensure the object is in the graph, then it's contents are overridden with the scalar properties on the supplied object.
You might need an explicit cast on data_json to ensure it is of the same type contained in the entity set.
Using an ExpandoObject would allow you to send in only the properties you want to set, and would allow you to specify null values as well.
For example:
public static void updateTable(int id, dynamic data){
using(var context = new Entities()){
var obj = context.Table.Where(x=>x.id == id).FirstOrDefault();
if(obj != null){
if (((IDictionary<string, object>)data).ContainsKey("field1"))
obj.field1 = data.field1;
...
obj.SaveChanges();
}
}
}
and you could call it like this:
dynamic data = new ExpandoObject();
data.field1 = 123;
data.field2 = null;
data.field5 = "abc";
MyClass.updateTable(1, data);
Everything can be solved with a moment of reflection. This function solves the problem:
public void UpdateTable(int id, object values)
{
using (var entities = new MyEntities())
{
var valuesType = values.GetType();
var element = entities.MyTable.Where(t => t.ID == id).First();
//We are iterating through all properties of updated element and checking
//if there is value provided for there properties in values parameter
foreach (var property in element.GetType().GetProperties())
{
var valuesProperty = valuesType.GetProperty(property.Name);
//If values contain this property
if (valuesProperty != null)
{
//taking value out of values parameter
var value = valuesProperty.GetValue(values, null);
//setting it in our element to update
property.SetValue(element, value, null);
}
}
entities.SaveChanges();
}
}
Usage:
UpdateTable(125, new { FieldA = 1, FieldB = "ABCD" });
You can even make this method more universal by adding generic table type parameter.