I'm developping an application with c# and ADO .NET entity data model. I have a table Articles(idArticle, nameArticle, statusArticles). I want to retrieve the first article where statusArticle=false, and update her value to true. Someone can help me with this code please:
private void button_Click(object sender, EventArgs e)
{
using (DbEntities db = new DbEntities())
{
Articles firstArticle = db.Articles.FirstOrDefault(u => u.statusArticle == false);
if (firstArticle != null)
{
firstArticle.statusArticle = true;
MessageBox.Show("Article validated", "OK");
this.Refresh();
}
}
}
This can be done as follows
private void button_Click(object sender, EventArgs e)
{
using (DbEntities db = new DbEntities())
{
Articles firstArticle = db.Articles.FirstOrDefault(u => u.statusArticle == false);
// firstArticle is not null anyways as you are calling FirstOrDefault()
**EDIT** // In case nothing has status = false, you will get a new Articles object, so instead of the below null check, you have to check for other property like id or name that will be unique.
if (firstArticle != null)
{
firstArticle.statusArticle = true;
db.SaveChanges();
MessageBox.Show("Article validated", "OK");
this.Refresh();
}
}
}
.FirstOrDefault()
public static TSource FirstOrDefault<TSource>(
this IEnumerable<TSource> source //db.Articles
)
will return:
default(TSource) if source is empty; otherwise, the first element in source.
default(TSource) returns null for reference type elements or (usually) 0 for value type elements.
Your amended code:
private void button_Click(object sender, EventArgs e)
{
using (DbEntities db = new DbEntities())
{
Articles firstArticle = db.Articles.FirstOrDefault(u => u.statusArticle == false);
if (firstArticle != null)
{
firstArticle.statusArticle = true;
MessageBox.Show("Article validated", "OK");
db.SaveChanges(); //change (can go before/after validation message)
this.Refresh();
}
}
}
Related
Why doesn't the below code store one object into the array? I can't find my mistake. If the array has one object already, it should display another message.
Here is the C# code. I guess the XAML code isn't necessary. Perhaps my mistake is with NULL?
TraderInfos[] bossArray = new TraderInfos[1];
public Reset_Register()
{
InitializeComponent();
}
private void CheckPassword(object sender, RoutedEventArgs e)
{
if (bossArray != null)
{
if (SecurtyQuestionMother.Text == securityQ_mother_textbox.Text && SecurityQuestionSchool.Text == securityQ_school_texbox.Text)
{
foreach (var item in bossArray)
{
PasswordApears.Text = $"Your password is: {item.Password}";
}
}
else
{
PasswordApears.Text = "You've not found it";
}
}
else
{
MessageBox.Show("There isnt being any data stored yet");
}
}
private void SafeTheEntries(object sender, RoutedEventArgs e)
{
if (bossArray == null)
{
TraderInfos boss = new TraderInfos()
{
First_Name = first_name_textbox.Text,
Last_Name = last_name_textbox.Text,
Company_Name = company_name_textbox.Text,
Phonenumber = phonenumber_textbox.Text,
Password = passwordText.Text,
SecurityQuestionMother = securityQ_mother_textbox.Text,
SecurityQuestionSchool = securityQ_school_texbox.Text
};
bossArray[0] = boss;
MessageBox.Show($"dear {boss.First_Name}!\nYour data has been saved!");
}
else
{
MessageBox.Show("You can't enter more one entry!");
}
}
Your code creates the array at the top and, because of that, your array will not be null. The bossArray[0] should be equal to null, not bossArray.
So check
if (bossArray[0] != null)
or
if (bossArray[0] == null)
I have an active Google Places autocomplete working with Xamarin Forms or Cross Platform. I have a working solution that auto populates the address when the user types in the address. My problem is when the user selects it from the list the address does not go to the search_bar.text… The search bar just remains with the text that was typed? how can I get the text when selected to populate in the search bar.
I am new to Xamarin forms and C#.
public Createbusinessaccount ()
{
InitializeComponent ();
search_bar.ApiKey = GooglePlacesApiKey;
search_bar.Type = PlaceType.Address;
search_bar.Components = new Components("country:us"); // Restrict results to Australia and New Zealand
search_bar.PlacesRetrieved += Search_Bar_PlacesRetrieved;
search_bar.TextChanged += Search_Bar_TextChanged;
search_bar.MinimumSearchText = 2;
results_list.ItemSelected += Results_List_ItemSelected;
}
void Search_Bar_PlacesRetrieved(object sender, AutoCompleteResult result)
{
results_list.ItemsSource = result.AutoCompletePlaces;
spinner.IsRunning = false;
spinner.IsVisible = false;
if (result.AutoCompletePlaces != null && result.AutoCompletePlaces.Count > 0)
results_list.IsVisible = true;
}
void Search_Bar_TextChanged(object sender, TextChangedEventArgs e)
{
if (!string.IsNullOrEmpty(e.NewTextValue))
{
results_list.IsVisible = false;
spinner.IsVisible = true;
spinner.IsRunning = true;
}
else
{
results_list.IsVisible = true;
spinner.IsRunning = false;
spinner.IsVisible = false;
}
}
async void Results_List_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
if (e.SelectedItem == null)
return;
var prediction = (AutoCompletePrediction)e.SelectedItem;
results_list.SelectedItem = null;
var place = await Places.GetPlace(prediction.Place_ID, GooglePlacesApiKey);
if (place != null)
await DisplayAlert(
place.Name, string.Format("Lat: {0}\nLon: {1}", place.Latitude, place.Longitude), "OK");
}
In your ItemSelected method, you need to set the text of the searchbar:
async void Results_List_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
if (e.SelectedItem == null)
return;
var prediction = (AutoCompletePrediction)e.SelectedItem;
search_bar.Text = prediction.Name? // Your property here
results_list.SelectedItem = null;
var place = await Places.GetPlace(prediction.Place_ID, GooglePlacesApiKey);
if (place != null)
await DisplayAlert(
place.Name, string.Format("Lat: {0}\nLon: {1}", place.Latitude, place.Longitude), "OK");
}
I am still trying to fix this, it only adds the street name and number not the whole address
I have a LongListSelector that is populated with List which contains objects from SQLite database:
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
SQLiteAsyncConnection conn = new SQLiteAsyncConnection(DB_PATH);
var query = conn.Table<Prasanja>().Where(x => x.id == 3);
var result = await query.ToListAsync();
foreach (var item in result)
{
var query1 = conn.Table<Odgovori>()
.Where(y => y.Prasanja_id == item.id);
txtPrasanje.Text = item.Tekst;
var resultOdgovori = await query1.ToListAsync();
foreach (var itemOdgovor in resultOdgovori)
{
Lista.Add(itemOdgovor.Odgovor.ToString());
lstOdgovori.ItemsSource = Lista;
}
}
What I want is when one of the LongListSelector items is tapped that I get the specific object tapped, and have the ability to use that object properties.Here is my code:
private void lstOdgovori_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
LongListSelector selector = sender as LongListSelector;
if (selector == null)
return;
Odgovori odg = selector.SelectedItem as Odgovori;
if (odg == null)
return;
if(odg.Tocno==null)
MessageBox.Show("Try again");
else MessageBox.Show("True!!!");
}
The problem here is that my object odg from the class Odgovori returns null after executing this code. How can I fix this?
You are adding a string to Lista that is why your casting is not working. If you have overridden your ToString() method in your Odgovori class I believe that the LongListSelector will call that method if you just add the Odgovori object to Lista
My question comes from a problem which I have right now. I have MainWindow, AuthenticateWindow, and AddEntryWindow which all are WinForms. In main window I have possibility to Authenticate and Add Entry into my main windows textbox. They can not add an entry until they authenticate (no problem with this). I need to add an entry to the text box which will update my main windows textbox. The problem if, how can I check if entry was added to my textbox?
I am trying to have a Save option from menu strip. I am getting an error whenever I am trying to save an empty file. How could I authenticate the saving process by Save button by having it first disabled, and enabled after entry was added?
I could always verify if if textbox had an entry but I want to have button disabled first, and enabled after entry was added. I do not have a privilege to do so as of right now.
Please ask questions if I am not clear enough.
private void tsmiSave_Click(object sender, EventArgs e)
{
// Open sfdSaveToLocation which let us choose the
// location where we want to save the file.
if (txtDisplay.Text != string.Empty)
{
sfdSaveToLocation.ShowDialog();
}
}
MainWindow.cs
using System;
using System.IO;
using System.Windows.Forms;
namespace Store_Passwords_and_Serial_Codes
{
public partial class MainWindow : Form
{
private AuthenticateUser storedAuth;
public MainWindow()
{
InitializeComponent();
}
private void MainWindow_Load(object sender, EventArgs e)
{
// Prohibit editing.
txtDisplay.Enabled = false;
}
public string ChangeTextBox
{
get
{
return this.txtDisplay.Text;
}
set
{
this.txtDisplay.Text = value;
}
}
private void tsmiAuthenticate_Click(object sender, EventArgs e)
{
AuthenticationWindow authWindow = new AuthenticationWindow();
authWindow.ShowDialog();
storedAuth = authWindow.Result;
}
private void tsmiAddEntry_Click(object sender, EventArgs e)
{
if (storedAuth == null)
{
DialogResult result = MessageBox.Show
("You must log in before you add an entry."
+ Environment.NewLine + "You want to authenticate?",
"Information", MessageBoxButtons.YesNo,
MessageBoxIcon.Information);
if (result == DialogResult.Yes)
{
AuthenticationWindow authWindow =
new AuthenticationWindow();
authWindow.ShowDialog();
storedAuth = authWindow.Result;
AddEntryWindow addWindow = new AddEntryWindow
(this, storedAuth.UserName, storedAuth.Password);
addWindow.ShowDialog();
}
}
else
{
AddEntryWindow addWindow = new AddEntryWindow
(this, storedAuth.UserName, storedAuth.Password);
addWindow.ShowDialog();
}
}
private void tsmiClose_Click(object sender, EventArgs e)
{
this.Close();
}
private void tsmiSave_Click(object sender, EventArgs e)
{
// Open sfdSaveToLocation which let us choose the
// location where we want to save the file.
sfdSaveToLocation.ShowDialog();
}
private void sfdSaveToLocation_FileOk(object sender, System.ComponentModel.CancelEventArgs e)
{
string theFileName = sfdSaveToLocation.FileName;
EncryptDecrypt en = new EncryptDecrypt();
string encrypted = en.Encrypt(txtDisplay.Text,
storedAuth.UserName, storedAuth.Password);
MessageBox.Show(encrypted);
File.WriteAllText(theFileName, encrypted);
}
}
}
AddEntryWindow.cs
using System;
using System.Windows.Forms;
// Needed to be used with StringBuilder
using System.Text;
// Needed to be used with ArrayList.
using System.Collections;
namespace Store_Passwords_and_Serial_Codes
{
public partial class AddEntryWindow : Form
{
string user, pass;
// Initializind ArrayList to store all data needed to be added or retrived.
private ArrayList addedEntry = new ArrayList();
// Initializing MainWindow form.
MainWindow mainWindow;
// Default constructor to initialize the form.
public AddEntryWindow()
{
InitializeComponent();
}
public AddEntryWindow(MainWindow viaParameter, string user, string pass)
: this()
{
mainWindow = viaParameter;
this.user = user;
this.pass = pass;
}
private void AddEntryWindow_Load(object sender, EventArgs e)
{ }
private void btnAddEntry_Click(object sender, EventArgs e)
{
// Making sure that type is selected.
if (cmbType.SelectedIndex == -1)
{
MessageBox.Show("Please select entry type!", "Error!",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
// Each field must be filled for specified type.
// Here we are checking if all fields were filled.
else if ((cmbType.SelectedIndex == 0 && (txtUserName.Text == string.Empty || txtPassword.Text == string.Empty)) ||
(cmbType.SelectedIndex == 1 && (txtURL.Text == string.Empty || txtPassword.Text == string.Empty)) ||
(cmbType.SelectedIndex == 2 && (txtSoftwareName.Text == string.Empty || txtSerialCode.Text == string.Empty)))
{
MessageBox.Show("Please fill all the fields!", "Error!",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
{
int totalEntries = 0;
if(cmbType.SelectedIndex == 0)
addedEntry.Add(new AddPC(cmbType.Text,
txtUserName.Text, txtPassword.Text));
else if(cmbType.SelectedIndex == 1)
addedEntry.Add(new AddWebSite(cmbType.Text,
txtUserName.Text, txtPassword.Text, txtURL.Text));
else if(cmbType.SelectedIndex == 2)
addedEntry.Add(new AddSerialCode(cmbType.Text,
txtSoftwareName.Text, txtSerialCode.Text));
StringBuilder stringBuilder = new StringBuilder();
foreach (var list in addedEntry)
{
if (list is AddPC)
{
totalEntries++;
AddPC tmp = (AddPC)list;
stringBuilder.Append(tmp.ToString());
}
else if (list is AddWebSite)
{
totalEntries++;
AddWebSite tmp = (AddWebSite)list;
stringBuilder.Append(tmp.ToString());
}
else if (list is AddSerialCode)
{
totalEntries++;
AddSerialCode tmp = (AddSerialCode)list;
stringBuilder.Append(tmp.ToString());
}
}
mainWindow.ChangeTextBox = stringBuilder.ToString();
mainWindow.tsslStatus.Text = "A total of " + totalEntries + " entries added.";
// Clearing all fields.
ClearFields();
}
}
private void btnClear_Click(object sender, EventArgs e)
{
ClearFields();
}
private void btnClose_Click(object sender, EventArgs e)
{
// Closing the Add Entry Window form.
this.Close();
}
private void cmbType_SelectedIndexChanged(object sender, EventArgs e)
{
// Deciding which data must be entered depending on
// what type is selected from combo box.
// PC
if (cmbType.SelectedIndex == 0)
{}
// Web Site
else if (cmbType.SelectedIndex == 1)
{}
// Serial Code
else if (cmbType.SelectedIndex == 2)
{}
}
private void ClearFields()
{
// Clearing all fields to the default state.
}
}
}
Regards.
It sounds like you probably just want to subscribe to the TextChanged event, which will be fired whenever the text in the textbox changes.
I can't say I really followed everything that you're doing, but I think you should be fine to just enable or disable your Save button within that event handler.
EDIT: It's not really clear where all your different components live, but you want something like:
// Put this after the InitializeComponent() call in the constructor.
txtDisplay.TextChanged += HandleTextBoxTextChanged;
...
private void HandleTextBoxTextChanged(object sender, EventArgs e)
{
bool gotText = txtDisplay.Text.Length > 0;
menuSaveButton.Enabled = gotText;
}
I'd also strongly advise you not to use ArrayList but to use the generic List<T> type. The non-generic collections should almost never be used in new code.
I'm trying to implement database value edition through a DataGridView control but honestly I'm having a hard time trying to accomplish that. I'm basically using LINQ-to-SQL classes and events, the following being the most significant snippets:
var data = from q in data.FOOBARS
select new
{
ID = q.FOOBAR_ID,
LOREM = q.FOOBAR_LOREM,
IPSUM = q.FOOBAR_IPSUM
};
DataGridView grid = new DataGridView();
grid.DataSource = data;
// grid EVENTS
private void grid_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
{
this.grid.CurrentCell.ReadOnly = false;
this.grid.BeginEdit(true);
}
private void grid_CellLeave(object sender, DataGridViewCellEventArgs e)
{
if (this.grid.CurrentCell.IsInEditMode)
{
// METHOD CALL
this.SetVariableValue(this.grid.CurrentRow.Cells["ID"].Value.ToString(), this.grid.CurrentCell.OwningColumn.Name, this.grid.CurrentCell.FormattedValue.ToString(), this.grid.CurrentCell.EditedFormattedValue.ToString());
}
this.grid.CommitEdit(DataGridViewDataErrorContexts.Commit);
this.grid.EndEdit();
}
// METHOD IMPL
private void SetVariableValue(string id, string type, string current, string edited)
{
try
{
if (current != edited)
{
using (FOOBARDataClassesDataContext data = new FOOBARDataClassesDataContext(this.BuildConnection()))
{
data.ExecuteCommand("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED");
switch (type)
{
case "LOREM":
var currentLorem = data.FOOBARS.SingleOrDefault(v => v.FOOBAR_ID == Convert.ToInt32(id)).FOOBAR_LOREM;
currentLorem = edited;
data.SubmitChanges(ConflictMode.ContinueOnConflict);
break;
case "IPSUM":
var currentIpsum = data.FOOBARS.SingleOrDefault(v => v.FOOBAR_ID == Convert.ToInt32(id)).FOOBAR_IPSUM;
currentIpsum = edited;
data.SubmitChanges(ConflictMode.ContinueOnConflict);
break;
default:
break;
}
data.Refresh(RefreshMode.OverwriteCurrentValues);
}
}
}
catch (Exception error)
{
if (logger.IsErrorEnabled) logger.Error(error.Message);
}
}
Debugging looks good, objects are actually being updated but for some reason changes are neither being submitted nor updated.
Any help would be certainly appreciated. Thanks much you guys in advance!
For some reason this does NOT WORK:
var currentLorem = data.FOOBARS.SingleOrDefault(v => v.FOOBAR_ID == Convert.ToInt32(id)).FOOBAR_LOREM;
currentLorem = edited;
data.SubmitChanges(ConflictMode.ContinueOnConflict);
But this DOES (notice the changes in lines 1 and 2, FOOBAR_LOREM attribute):
var currentLorem = data.FOOBARS.SingleOrDefault(v => v.FOOBAR_ID == Convert.ToInt32(id));
currentLorem.FOOBAR_LOREM = edited;
data.SubmitChanges(ConflictMode.ContinueOnConflict);