I have a class and I am using it inside a LIST
List<user> listWithCustomClass = List<user>();
myClass.cs
public class user
{
public user(string fullname, string city, string state, int age, int type)
{
name = fullname;
citi = city;
estate = state;
tipe = type;
}
private string name = string.Empty;
private string citi = string.Empty;
private string estate = string.Empty;
private int tipe = 0;
public string getFullname
{
get { return name; }
set { name = value;}
}
public string getCity
{
get { return citi; }
set { citi = value;}
}
public string getState
{
get { return state; }
set { state = value;}
}
public int getType
{
get { return type; }
set { type = value;}
}
}
How can I add a custom toString() without having to override generic toString(). I would like to add something like showDate().
For example, in a combobox I would like the output of the inserted information to be:
--> Hello, your name is {name} and your age is {age}
Like this:
foreach(var item in user)
{
user.ShowData();
}
Add this in your class:
public string ShowData()
{
return "Hello, your name is " + name + " and your age is " + age.ToString();
}
but you must also define age first. Which, following your style, would be:
private int age = 0;
and then in the constructor add:
this.age = age;
EDIT
foreach(var item in listWithCustomClass)
{
item.ShowData();
}
I made a custom usercontrol which contains a label.
I have 3 string properties : firstName, lastName, fullName.
How can I set the label's text = FullName ?
public string firstName
{
get; set;
}
public string lastName
{
get; set;
}
public string fullName //this fails
{
get { return string.Format("{0} {1}", firstName, lastName); }
set { labelFullName.Text = value; }
}
Looks like Windows Form to me. In WPF you would be using labelFullName.Content property. Assuming you want to set the label as the fullname each time first name or last name changes, then one option would be to do this within your UserControl class:
private String _sFirstName = "";
private String _sLastName = "";
public String FirstName {
get { return _sFirstName; }
set { _sFirstName = value; UpdateLabel(); }
}
public String LastName {
get { return _sLastName; }
set { _sLastName = value; UpdateLabel(); }
}
public String FullName {
get { return _sFirstName + " " + _sLastName; }
}
private void UpdateLabel() {
// do within a UI thread to prevent threading issues
this.BeginInvoke((Action)(() => {
labelFullName.Text = this.FullName.Trim();
}));
}
I am trying to get and send a list of this object to a text file. The text file is in the following format.
name,IDnumber,department,value
there are quite a few lines of this so i used a for to read them in.
This is the code for the read and write to the file.
public List<Employee> ReadFile(string fileName) {
StreamReader fileIn = new StreamReader(fileName);
fileIn = File.OpenText(fileName);
List<Employee> list = new List<Employee>();
string[] test;
string name;
string ID;
string dep;
string post;
while (!fileIn.EndOfStream || !File.Exists(fileName)) {
string inString = fileIn.ReadLine();
test = inString.Split('#');
name = test[0];
ID = test[1];
dep = test[2];
post = test[3];
Employee newEmp = new Employee(name, ID, dep, post);
list.Add(newEmp);
}
fileIn.Close();
return list;
}
public void WriteFile(List<Employee> outList, string file) {
StreamWriter writeOut = new StreamWriter(file);
for (int i = 0; i < outList.Count; i++) {
writeOut.WriteLine(outList[i].name + '#' + outList[i].IDnum + '#' + outList[i].department + '#' + outList[i].position);
}
writeOut.close();
}
This is the code for my class. The error is being thrown at the set.
public class Employee {
public string name { get { return name; } set { name = value; } }
public string IDnum { get { return IDnum; } set { IDnum = value; } }
public string department { get { return department; } set { department = value; } }
public string position { get { return position; } set { position = value; } }
public Employee() {
name = string.Empty;
IDnum = string.Empty;
department = string.Empty;
position = string.Empty;
}
public Employee(string newName, string newID) {
name = newName;
IDnum = newID;
department = string.Empty;
position = string.Empty;
}
public Employee(string newName, string newID, string newDep, string
newPost) {
name = newName;
IDnum = newID;
department = newPost;
position = newDep;
}
}
I am not sure if there is some kind of formatting that I am missing for the set function to function as needed. The This is the function i am calling for the in and out of the file. I believe that it is never making it to the out so it is likely how i am importing the data.
It's a really common gotcha... a C# rite of passage!
Let's take a look at a single property (this applies to all of your properties though)...
public string name { get { return name; } set { name = value; } }
so what happens when you try myObj.name = "foo";?
In the set method, you refer back to the very same property name. So it tries to access name, which goes around again (and again, and again, recursively until you StackOverflow).
A backing field with proper naming conventions is the norm here:
private string name;
public string Name{get { return name; } set{ name = value; }}
or even better, if there's no logic involved, an auto-property.
public string Name{ get; set; }
You keep calling IDnum and other properties over and over recursively, until the stack overflows
public string IDnum { get { return IDnum; } set { IDnum = value; } }
When you do something like
IDnum = someValue;
that calls the setter for IDnum, which runs the code in the setter
IDnum = value
Which in turn calls the setter of IDnum, until you run out of stack.
The Fix
In your case, it looks like you can use automatic properties
public string IDnum { get; set; }
You should change
public string name { get { return name; } set { name = value; } }
public string IDnum { get { return IDnum; } set { IDnum = value; } }
public string department { get { return department; } set { department = value; } }
public string position { get { return position; } set { position = value; } }
to
public string name { get; set; }
public string IDnum { get; set; }
public string department { get; set; }
public string position { get; set; }
or introduce backing fields:
private string _name;
public string name { get { return _name; } set { _name = value; } }
See https://msdn.microsoft.com/en-us/library/bb384054.aspx for more info on Auto-Implemented Properties in C#.
Please note, that the commonly used naming of public properties is PascalCasing. Your properties in PascalCasing would look like this:
public string Name { get; set; }
public string IdNum { get; set; }
public string Department { get; set; }
public string Position { get; set; }
I want to add a DisplayAttribute to the Client entity (from another project), but don't want to pollute my entity with attributes specific to MVC or a UI layer. So I planned to add the DisplayAttribute by applying a metadata class to a view model inheriting from the entity
If I inherit from the Client entity and then try to use the MetadataTypeAttribute to add a display attribute, it doesn't show up in the browser. Does anyone know how I can achieve the separation and the functionality of being able to add metadata to my entities?
The Client entity class:
public class Client
{
private string firstName;
private string lastName;
private string homeTelephone;
private string workTelephone;
private string mobileTelephone;
private string emailAddress;
private string notes;
public Title Title { get; set; }
public string FirstName
{
get { return this.firstName ?? string.Empty; }
set { this.firstName = value; }
}
public string LastName
{
get { return this.lastName ?? string.Empty; }
set { this.lastName = value; }
}
public string FullName
{
get
{
List<string> nameParts = new List<string>();
if (this.Title != Title.None)
{
nameParts.Add(this.Title.ToString());
}
if (this.FirstName.Length > 0)
{
nameParts.Add(this.FirstName.ToString());
}
if (this.LastName.Length > 0)
{
nameParts.Add(this.LastName.ToString());
}
return string.Join(" ", nameParts);
}
}
public Address Address { get; set; }
public string HomeTelephone
{
get { return this.homeTelephone ?? string.Empty; }
set { this.homeTelephone = value; }
}
public string WorkTelephone
{
get { return this.workTelephone ?? string.Empty; }
set { this.workTelephone = value; }
}
public string MobileTelephone
{
get { return this.mobileTelephone ?? string.Empty; }
set { this.mobileTelephone = value; }
}
public string EmailAddress
{
get { return this.emailAddress ?? string.Empty; }
set { this.emailAddress = value; }
}
public string Notes
{
get { return this.notes ?? string.Empty; }
set { this.notes = value; }
}
public Client()
{
this.Address = new Address();
}
}
The ClientViewModel view model class:
[MetadataType(typeof(ClientMetaData))]
public class ClientViewModel : Client
{
internal class ClientMetaData
{
[Display(ResourceType = typeof(ResourceStrings), Name = "Client_FirstName_Label")]
public string FirstName { get; set; }
}
}
I think you have change the typeof parameter to:
[MetadataType(typeof(ClientViewModel.ClientMetaData))]
public class ClientViewModel : Client
{
internal class ClientMetaData
{
[Display(ResourceType = typeof(ResourceStrings), Name = "Client_FirstName_Label")]
public string FirstName { get; set; }
}
}
For .Net Core 6.0 use
[ModelMetadataType(typeof(ClientViewModel.ClientMetaData))]
insead of
[MetadataType(typeof(ClientViewModel.ClientMetaData))]
I have this Business Layer/ Contactentry.ascx page which calls a stored prcoedure to insert data into sql database and then the page below calls this business layer method. the issue is this method
aspdotnet.BusinessLogicLayer.ContactEntry AddEntry =
new ContactEntry(Convert.ToInt32(Session["ContactID"].ToString())
,Title,FirstName,MiddleName,LastName,JobTitle,Company,Website,OfficePhone
,HomePhone,Mobile,Fax,OEmail,PEmail,OAStreet,OACity,OAState,OACountry
,OAZipCode,PAStreet,PACity,PAState,PACountry,PAZipCode);
throws an error saying object refernece not set to an instance of an object although I have entered all values for the text fields.
using System;
using System.Data;
using System.Configuration;
using aspdotnet.DataAccessLayer;
namespace aspdotnet.BusinessLogicLayer
{
public class ContactEntry
{
private int _ContactID;
private string _Title;
private string _FirstName;
private string _MiddleName;
private string _LastName;
private string _JobTitle;
private string _Company;
private string _Website;
private string _OfficePhone;
private string _HomePhone;
private string _Mobile;
private string _Fax;
private string _OEmail;
private string _PEmail;
private string _OAStreet;
private string _OACity;
private string _OAState;
private string _OACountry;
private string _OAZipCode;
private string _PAStreet;
private string _PACity;
private string _PAState;
private string _PACountry;
private string _PAZipCode;
public int ContactID
{
get { return _ContactID; }
set { _ContactID = value; }
}
public string Title
{
get { return _Title; }
set { _Title = value; }
}
public string FirstName
{
get { return _FirstName; }
set { _FirstName = value; }
}
public string MiddleName
{
get { return _MiddleName; }
set { _MiddleName = value; }
}
public string LastName
{
get { return _LastName; }
set { _LastName = value; }
}
public string JobTitle
{
get { return _JobTitle; }
set { _JobTitle = value; }
}
public string Company
{
get { return _Company; }
set { _Company = value; }
}
public string Website
{
get { return _Website; }
set { _Website = value; }
}
public string OfficePhone
{
get { return _OfficePhone; }
set { _OfficePhone = value; }
}
public string HomePhone
{
get { return _HomePhone; }
set { _HomePhone = value; }
}
public string Mobile
{
get { return _Mobile; }
set { _Mobile = value; }
}
public string Fax
{
get { return _Fax; }
set { _Fax = value; }
}
public string OEmail
{
get { return _OEmail; }
set { _OEmail = value; }
}
public string PEmail
{
get { return _PEmail; }
set { _PEmail = value; }
}
public string OAStreet
{
get { return _OAStreet; }
set { _OAStreet = value; }
}
public string OACity
{
get { return _OACity; }
set { _OACity = value; }
}
public string OAState
{
get { return _OAState; }
set { _OAState = value; }
}
public string OACountry
{
get { return _OACountry; }
set { _OACountry = value; }
}
public string OAZipCode
{
get { return _OAZipCode; }
set { _OAZipCode = value; }
}
public string PAStreet
{
get { return _PAStreet; }
set { _PAStreet = value; }
}
public string PACity
{
get { return _PACity; }
set { _PACity = value; }
}
public string PAState
{
get { return _PAState; }
set { _PAState = value; }
}
public string PACountry
{
get { return _PACountry; }
set { _PACountry = value; }
}
public string PAZipCode
{
get { return _PAZipCode; }
set { _PAZipCode = value; }
}
public ContactEntry()
{
}
public ContactEntry(int ContactID, string Title, string FirstName, string MiddleName, string LastName, string JobTitle, string Company, string Website, string OfficePhone, string HomePhone, string Mobile, string Fax, string OEmail, string PEmail, string OAStreet, string OACity, string OAState, string OACountry, string OAZipCode, string PAStreet, string PACity, string PAState, string PACountry, string PAZipCode)
{
_ContactID=ContactID;
_Title=Title;
_FirstName = FirstName;
_MiddleName = MiddleName;
_LastName = LastName;
_JobTitle = JobTitle;
_Company = Company;
_Website = Website;
_OfficePhone = OfficePhone;
_HomePhone = HomePhone;
_Mobile = Mobile;
_Fax = Fax;
_OEmail=OEmail;
_PEmail=PEmail;
_OAStreet = OAStreet;
_OACity = OACity;
_OAState = OAState;
_OACountry =OACountry;
_OAZipCode = OAZipCode;
_PAStreet = PAStreet;
_PACity = PACity;
_PAState = PAState;
_PACountry = PACountry;
_PAZipCode = PAZipCode;
}
public bool Save()
{
if (_ContactID == 0)
return Insert();
else
return Update();
}
private bool Insert()
{
_ContactID = Convert.ToInt32(DBTask.ExecuteScalar(System.Configuration.ConfigurationManager.AppSettings[Web.Global.CfgKeyConnString], "ContactInfo_Insert", _Title, _FirstName, _MiddleName, _LastName, _JobTitle, _Company, _Website, _OfficePhone, _HomePhone, _Mobile, _Fax, _OEmail, _PEmail, _OAStreet, _OACity, _OAState, _OACountry, _OAZipCode, _PAStreet, _PACity, _PAState, _PACountry, _PAZipCode));
return (0 < _ContactID);
}
public static void Remove(int ContactID)
{
DBTask.ExecuteNonQuery(System.Configuration.ConfigurationManager.AppSettings[Web.Global.CfgKeyConnString], "ContactInfo_Delete", ContactID);
}
private bool Update()
{
try
{
DBTask.ExecuteNonQuery(System.Configuration.ConfigurationManager.AppSettings[Web.Global.CfgKeyConnString], "ContactInfo_Update", _ContactID, _Title, _FirstName, _MiddleName, _LastName, _JobTitle, _Company, _Website, _OfficePhone, _HomePhone, _Mobile, _Fax, _OEmail, _PEmail, _OAStreet, _OACity, _OAState, _OACountry, _OAZipCode, _PAStreet, _PACity, _PAState, _PACountry, _PAZipCode);
return true;
}
catch
{
return false;
}
}
public void LoadContact(int ContactID)
{
DataSet ds = DBTask.ExecuteDataset(System.Configuration.ConfigurationManager.AppSettings[Web.Global.CfgKeyConnString], "ContactInfo_GetContact", ContactID);
DataRow row = ds.Tables[0].Rows[0];
_ContactID=Convert.ToInt32(row["ContactID"].ToString());
_Title=row["Title"].ToString();
_FirstName = row["FirstName"].ToString();
_MiddleName = row["MiddleName"].ToString();
_LastName = row["LastName"].ToString();
_JobTitle = row["JobTitle"].ToString();
_Company = row["Company"].ToString();
_Website = row["Website"].ToString();
_OfficePhone = row["OfficePhone"].ToString();
_HomePhone = row["HomePhone"].ToString();
_Mobile = row["Mobile"].ToString();
_Fax = row["Fax"].ToString();
_OEmail=row["OfficialEmail"].ToString();
_PEmail=row["PersonalEmail"].ToString();
_OAStreet = row["OAStreet"].ToString();
_OACity = row["OACity"].ToString();
_OAState = row["OAState"].ToString();
_OACountry =row["OACountry"].ToString();
_OAZipCode = row["OAZip"].ToString();
_PAStreet = row["PAStreet"].ToString();
_PACity = row["PACity"].ToString();
_PAState = row["PAState"].ToString();
_PACountry = row["PACountry"].ToString();
_PAZipCode = row["PAZip"].ToString();
}
}
}
Insert form calling above function from Business Layer:
private void btnSave_Click(object sender, System.EventArgs e)
{
string Title = drplstTitle.SelectedItem.Text;
string FirstName = txtFirstName.Text;
string MiddleName = txtMiddleName.Text;
string LastName = txtLastName.Text;
string JobTitle = this.txtJobTitle.Text;
string Company = this.txtCompany.Text;
string Website = this.txtWebSite.Text;
string OfficePhone = this.txtOfficePhone.Text;
string HomePhone = this.txtHomePhone.Text;
string Mobile = this.txtMobile.Text;
string Fax = this.txtFax.Text;
string OEmail = this.txtOfficialEmail.Text;
string PEmail = this.txtPersonalEmail.Text;
string OAStreet = this.txtOAStreet.Text;
string OACity = this.txtOACity.Text ;
string OAState = this.txtOAState.Text;
string OACountry = this.txtOACountry.Text;
string OAZipCode = this.txtOAZipCode.Text;
string PAStreet = this.txtPAStreet.Text;
string PACity = this.txtPACity.Text;
string PAState = this.txtPAState.Text;
string PACountry = this.txtPACountry.Text;
string PAZipCode = this.txtPAZipCode.Text;
aspdotnet.BusinessLogicLayer.ContactEntry AddEntry =
new ContactEntry(Convert.ToInt32(Session["ContactID"].ToString()),Title,FirstName,MiddleName,LastName,JobTitle,Company,Website,OfficePhone,HomePhone,Mobile,Fax,OEmail,PEmail,OAStreet,OACity,OAState,OACountry,OAZipCode,PAStreet,PACity,PAState,PACountry,PAZipCode);
//AddEntry.Save();
}
I get object reference not set to an insance of object right after above method aspdotnet.BusinessLogicLayer.ContactEntry above. I see all values are being passed when I am debugging. I entered all values when entering values above but it still errors out. Not sure what I am missing. Please help , appreciate your time.
This line is suspicious:
Convert.ToInt32(Session["ContactID"].ToString())
Session["ContactID"] may return null and calling ToString() on null blows up. Convert.ToInt32(null) wouldn't throw an error - it would return 0, not NULL.
You to handle Session["ContactID"] for nulls and Empty before Converting it to Int32
Example :
ContactEntry cEntry = null;
if(Session["ContactID"] != null)
{
if(!String.IsNullOrEmpty(Session["ContactID"]))
{
cEntry = new ContactEntry(Convert.ToInt32(Session["ContactID"].ToString());
}
}
Check your Session["ContactID"].
Consider changing your code to something like this...
//...
string PAState = this.txtPAState.Text;
string PACountry = this.txtPACountry.Text;
string PAZipCode = this.txtPAZipCode.Text;
string contactIDstr = Session["ContactID"] as string;
int contactID = 0;
if(!String.IsNullOrEmpty(conactIDStr))
Int32.TryParse(contactIDStr, out contactID);
aspdotnet.BusinessLogicLayer.ContactEntry AddEntry = new ContactEntry(
contentID,
Title,
FirstName,MiddleName,LastName,JobTitle,Company,
Website,OfficePhone,HomePhone,Mobile,Fax,OEmail,PEmail,
OAStreet,OACity,OAState,OACountry,OAZipCode,PAStreet,PACity,PAState,PACountry,PAZipCode
);