Develop Reference

Xamarin studio UIImageView

I can load a picture to a UImageView with I click a button, but not from a timer. why is that ? and how can I fix it ?
here is my code :
void _timer_Elapsed(object sender, ElapsedEventArgs e)
{
Patter_Function();
switch_Function();
}
void switch_Function()
{
image1 = new UIImage();
image1 = UIImage.FromBundle("heart");
image2 = new UIImage();
image2 = UIImage.FromFile( #"White_Sharingan.png");
image3 = new UIImage();
image3 = UIImage.FromFile("snow.png");
image4 = new UIImage();
//image4.//FromFile("Images/waterfront.jpg");
switch (Patter_1[switch_Counter].Move0) {
case 0 :
Box_1.Image = image1;
break;
case 1 :
Box_1.Image = image1;
break;
case 2 :
Box_2.Image = image1;
break;
case 3:
Box_3.Image = image1;
break;
case 4:
Box_4.Image = image1;
break;
case 5:
Box_5.Image = image1;
break;
case 6:
Box_6.Image = image1;
break;
case 7:
Box_7.Image = image1;
break;
case 8:
Box12.Image = image1;
break;
case 9:
Box_9.Image = image1;
break;
case 10:
Box_10.Image = image1;
break;
case 11:
Box_11.Image = image1;
break;
case 12:
Box8.Image = image1;
break;
case 13:
Box_13.Image = image1;
break;
case 14:
Box_14.Image = image1;
break;
case 15:
Box_15.Image = image1;
break;
case 16:
Box_16.Image = image1;
break;
case 17:
Box_17.Image = image1;
break;
case 18:
Box_18.Image = image1;
break;
case 19:
Box_19.Image = image1;
break;
case 20:
Box_20.Image = image1;
break;}
switch (Patter_1[switch_Counter].Move1)
{
case 0:
Box_1.Image = image2;
break;
case 1:
Box_2.Image = image2;
break;
case 2:
Box_2.Image = image2;
break;
case 3:
Box_3.Image = image2;
break;
case 4:
Box_4.Image = image2;
break;
case 5:
Box_5.Image = image2;
break;
case 6:
Box_6.Image = image2;
break;
case 7:
Box_7.Image = image2;
break;
case 8:
Box12.Image = image2;
break;
case 9:
Box_9.Image = image2;
break;
case 10:
Box_10.Image = image2;
break;
case 11:
Box_11.Image = image2;
break;
case 12:
Box8.Image = image2;
break;
case 13:
Box_13.Image = image2;
break;
case 14:
Box_14.Image = image2;
break;
case 15:
Box_15.Image = image2;
break;
case 16:
Box_16.Image = image2;
break;
case 17:
Box_17.Image = image2;
break;
case 18:
Box_18.Image = image2;
break;
case 19:
Box_19.Image = image2;
break;
case 20:
Box_20.Image = image2;
break;
}
switch (Patter_1[switch_Counter].Move2)
{
case 0:
Box_1.Image = image3;
break;
case 1:
Box_2.Image = image3;
break;
case 2:
Box_2.Image = image3;
break;
case 3:
Box_3.Image = image3;
break;
case 4:
Box_4.Image = image3;
break;
case 5:
Box_5.Image = image3;
break;
case 6:
Box_6.Image = image3;
break;
case 7:
Box_7.Image = image3;
break;
case 8:
Box12.Image = image3;
break;
case 9:
Box_9.Image = image3;
break;
case 10:
Box_10.Image = image3;
break;
case 11:
Box_11.Image = image3;
break;
case 12:
Box8.Image = image3;
break;
case 13:
Box_13.Image = image3;
break;
case 14:
Box_14.Image = image3;
break;
case 15:
Box_15.Image = image3;
break;
case 16:
Box_16.Image = image3;
break;
case 17:
Box_17.Image = image3;
break;
case 18:
Box_18.Image = image3;
break;
case 19:
Box_19.Image = image3;
break;
case 20:
Box_20.Image = image3;
break;
}
switch (Patter_1[switch_Counter].Move3)
{
case 0:
Box_1.Image = image4;
break;
case 1:
Box_2.Image = image4;
break;
case 2:
Box_2.Image = image4;
break;
case 3:
Box_3.Image = image4;
break;
case 4:
Box_4.Image = image4;
break;
case 5:
Box_5.Image = image4;
break;
case 6:
Box_6.Image = image4;
break;
case 7:
Box_7.Image = image4;
break;
case 8:
Box12.Image = image4;
break;
case 9:
Box_9.Image = image4;
break;
case 10:
Box_10.Image = image4;
break;
case 11:
Box_11.Image = image4;
break;
case 12:
Box8.Image = image4;
break;
case 13:
Box_13.Image = image4;
break;
case 14:
Box_14.Image = image4;
break;
case 15:
Box_15.Image = image4;
break;
case 16:
Box_16.Image = image4;
break;
case 17:
Box_17.Image = image4;
break;
case 18:
Box_18.Image = image4;
break;
case 19:
Box_19.Image = image4;
break;
case 20:
Box_20.Image = image4;
break;
}
switch_Counter++;
if (switch_Counter >4 )
{
switch_Counter = 0;
}
}
I used the debugger, so I know the code is getting to the line
but it is not doing anything when it get there
the bebugger says:
UIKit.UIKitThreadAccessException: UIKit Consistency error: you are calling a UIKit method that can only be invoke from the UI Thread.
Is there a why around that ?

Any operation you involve in modifying UI view, you will need to do it under UI/Main thread. So put the code inside the lambda of:
InvokeOnMainThread ( () => {
// manipulate UI controls
});

Passing a variable from a method to a button click event

I want to be able to pass upperEncodedMsg into the text property of msgLabel at the bottom of my code.
namespace ProgrammingAssignmentDecoder
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public void Encode()
{
string message = Convert.ToString(messageTxt.Text);
char[] encodeArray = message.ToCharArray();
for (int i = 0; i < encodeArray.Length; i++)
{
char letter = (encodeArray[i]);
switch (letter)
{
case 'a':
case 'A':
encodeArray[i] = 't';
break;
case 'b':
case 'B':
encodeArray[i] = 'u';
break;
case 'c':
case 'C':
encodeArray[i] = 'v';
break;
case 'd':
case 'D':
encodeArray[i] = 'w';
break;
case 'e':
case 'E':
encodeArray[i] = 'x';
break;
case 'f':
case 'F':
encodeArray[i] = 'y';
break;
case 'g':
case 'G':
encodeArray[i] = 'z';
break;
case 'h':
case 'H':
encodeArray[i] = 'a';
break;
case 'i':
case 'I':
encodeArray[i] = 'b';
break;
case 'j':
case 'J':
encodeArray[i] = 'c';
break;
case 'k':
case 'K':
encodeArray[i] = 'd';
break;
case 'l':
case 'L':
encodeArray[i] = 'e';
break;
case 'm':
case 'M':
encodeArray[i] = 'f';
break;
case 'n':
case 'N':
encodeArray[i] = 'g';
break;
case 'o':
case 'O':
encodeArray[i] = 'h';
break;
case 'p':
case 'P':
encodeArray[i] = 'i';
break;
case 'q':
case 'Q':
encodeArray[i] = 'j';
break;
case 'r':
case 'R':
encodeArray[i] = 'k';
break;
case 's':
case 'S':
encodeArray[i] = 'l';
break;
case 't':
case 'T':
encodeArray[i] = 'm';
break;
case 'u':
case 'U':
encodeArray[i] = 'n';
break;
case 'v':
case 'V':
encodeArray[i] = 'o';
break;
case 'w':
case 'W':
encodeArray[i] = 'p';
break;
case 'x':
case 'X':
encodeArray[i] = 'q';
break;
case 'y':
case 'Y':
encodeArray[i] = 'r';
break;
case 'z':
case 'Z':
encodeArray[i] = 's';
break;
}
}
}
static string upperEncoded(char[] encodeArray, string upperEncodedMsg)
{
string encodedMsg = new string(encodeArray);
upperEncodedMsg = encodedMsg.ToUpper();
return upperEncodedMsg;
}
private void clearBtn_Click(object sender, EventArgs e)
{
messageTxt.Text = string.Empty;
msgLabel.Text = string.Empty;
processedMessageLabel.Text = "Processed Message: ";
}
private void encodeBtn_Click(object sender, EventArgs e)
{
Encode();
if (messageTxt.TextLength == 0)
{
MessageBox.Show("There is no message to Encode");
}
else
{
processedMessageLabel.Text = "Encoded Message: ";
msgLabel.Visible = true;
}
msgLabel.Text = upperEncodedMsg;
}
}
}

I tried to keep your structure in tact, there are a few things that could be done in less characters and in less complicated ways, but as you are learning the language practice is the only thing that can improve your skills :) So well done.
namespace ProgrammingAssignmentDecoder
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private string upperEncodedMsg = null;
public void Encode()
{
string message = Convert.ToString(messageTxt.Text);
char[] encodeArray = message.ToCharArray();
for (int i = 0; i < encodeArray.Length; i++)
{
char letter = (encodeArray[i]);
switch (letter)
{
case 'a':
case 'A':
encodeArray[i] = 't';
break;
case 'b':
case 'B':
encodeArray[i] = 'u';
break;
case 'c':
case 'C':
encodeArray[i] = 'v';
break;
case 'd':
case 'D':
encodeArray[i] = 'w';
break;
case 'e':
case 'E':
encodeArray[i] = 'x';
break;
case 'f':
case 'F':
encodeArray[i] = 'y';
break;
case 'g':
case 'G':
encodeArray[i] = 'z';
break;
case 'h':
case 'H':
encodeArray[i] = 'a';
break;
case 'i':
case 'I':
encodeArray[i] = 'b';
break;
case 'j':
case 'J':
encodeArray[i] = 'c';
break;
case 'k':
case 'K':
encodeArray[i] = 'd';
break;
case 'l':
case 'L':
encodeArray[i] = 'e';
break;
case 'm':
case 'M':
encodeArray[i] = 'f';
break;
case 'n':
case 'N':
encodeArray[i] = 'g';
break;
case 'o':
case 'O':
encodeArray[i] = 'h';
break;
case 'p':
case 'P':
encodeArray[i] = 'i';
break;
case 'q':
case 'Q':
encodeArray[i] = 'j';
break;
case 'r':
case 'R':
encodeArray[i] = 'k';
break;
case 's':
case 'S':
encodeArray[i] = 'l';
break;
case 't':
case 'T':
encodeArray[i] = 'm';
break;
case 'u':
case 'U':
encodeArray[i] = 'n';
break;
case 'v':
case 'V':
encodeArray[i] = 'o';
break;
case 'w':
case 'W':
encodeArray[i] = 'p';
break;
case 'x':
case 'X':
encodeArray[i] = 'q';
break;
case 'y':
case 'Y':
encodeArray[i] = 'r';
break;
case 'z':
case 'Z':
encodeArray[i] = 's';
break;
}
}
foreach (char eachChar in encodeArray) {
upperEncodedMsg += eachChar;
}
}
public void upperEncoded()
{
if (upperEncodedMsg != null)
{ upperEncodedMsg = upperEncodedMsg.ToUpper(); }
}
private void clearBtn_Click(object sender, EventArgs e)
{
messageTxt.Text = string.Empty;
msgLabel.Text = string.Empty;
processedMessageLabel.Text = "Processed Message: ";
}
private void encodeBtn_Click(object sender, EventArgs e)
{
if (messageTxt.TextLength == 0)
{
MessageBox.Show("There is no message to Encode");
}
else
{
Encode();
upperEncoded();
processedMessageLabel.Text = "Encoded Message: ";
msgLabel.Visible = true;
}
msgLabel.Text = upperEncodedMsg;
}
}
}

I'd go down the route of creating a mapping using a Dictionary<char, char>(see here for details on Dictionary) and simply lookup the key value in the dictionary for each char in encodeArray. It may also be better to use a StringBuilder rather than just a string to store your encoded message.
Create Mapping
//Add Dictionary at the top of the class along with upperEncodedMsg string.
private Dictionary<char, char> charMapping;
private StringBuilder upperEncodedMsg;
//Create mappings. Use uppercase values here and you won't need to use your 'upperEncoded' method. This bit can be done in your Form1 constructor.
public Form1()
{
InitializeComponent();
charMapping = new Dictionary<char, char>();
charMapping.Add('A', 'T');
charMapping.Add('B', 'U');
//more mappings...
}
You can then remove the big switch statement you have and replace it with the following:
public void Encode()
{
upperEncodedMsg = new StringBuilder();
string message = Convert.ToString(messageTxt.Text);
char[] encodeArray = message.ToUpper().ToCharArray();
for(int i = 0; i < encodeArray.Length; i++)
{
//Use the mappings created earlier to get the associated char.
char outputLetter;
charMapping.TryGetValue(encodeArray[i], out outputLetter);
//Append letter to your upperEncodedMsg StringBuilder.
upperEncodedMsg.Append(outputLetter);
}
}
In your button click, at the bottom you can then add:
private void encodeBtn_Click(object sender, EventArgs e)
{
//your code...
msgLabel.Text = upperEncodedMsg.ToString();
}
The main benefit of doing it this way is that your mappings can be made available in other parts of your code. It also makes it easier to maintain and your mappings are loaded as soon as the form is, rather than waiting to call your encode method. A lookup of a Dictionary is also likely to be quicker than a large switch statement.

Switch case statement

I am trying to create an application in C# that converts numbers in a text box to roman numerals in a label control and need to use a case statement. However one of my variable Roman gets the error message: Use of unassigned local variable 'Roman'.
Here is my code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Roman_Numeral_Converter
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnCalc_Click(object sender, EventArgs e)
{
int Number=int.Parse(txtNum.Text); // To hold Number
string Roman; // To hold Roman Numeral
if (Number>=1 && Number <=10)
{
switch (Roman)
{
case "Number==1":
lblRoman.Text = "I";
break;
case "Number==2":
lblRoman.Text = "II";
break;
case "Number==3":
lblRoman.Text = "III";
break;
case "Number==4":
lblRoman.Text = "IV";
break;
case "Number==5":
lblRoman.Text = "V";
break;
case "Number==6":
lblRoman.Text = "VI";
break;
case "Number==7":
lblRoman.Text = "VII";
break;
case "Number==8":
lblRoman.Text = "VIII";
break;
case "Number==9":
lblRoman.Text = "IX";
break;
case "Number==10":
lblRoman.Text = "X";
break;
}
}
else
{
MessageBox.Show("Error: Invalid Input");
}
}
private void btnExit_Click(object sender, EventArgs e)
{
// Close the form.
this.Close();
}
private void btnClear_Click(object sender, EventArgs e)
{
txtNum.Text = "";
lblRoman.Text = "";
}
}
}

Your structure is a little off.
private void btnCalc_Click(object sender, EventArgs e)
{
var Number = int.Parse(txtNum.Text); // To hold Number
switch (Number)
{
case 1:
lblRoman.Text = "I";
break;
case 2:
lblRoman.Text = "II";
break;
case 3:
lblRoman.Text = "III";
break;
case 4:
lblRoman.Text = "IV";
break;
case 5:
lblRoman.Text = "V";
break;
case 6:
lblRoman.Text = "VI";
break;
case 7:
lblRoman.Text = "VII";
break;
case 8:
lblRoman.Text = "VIII";
break;
case 9:
lblRoman.Text = "IX";
break;
case 10:
lblRoman.Text = "X";
break;
default:
MessageBox.Show("Error: Invalid Input");
break;
}
}
You're using the lblRoman to hold your result, thus your Roman variable is unnecessary. Additionally, since you're interrogating every possible valid number in your switch, you can just use the default to replace your if/else structure.
I'm assuming you're doing this as an academic exercise. That being said, I would be remiss not to point to you Mosè Bottacini's solution to this problem.

This is because Roman variable is really unassigned. You should assign it before you enter the statement

try this,
when your number value like 1 so roman number is I.
private void btnCalc_Click(object sender, EventArgs e)
{
int Number = int.Parse(txtNum.Text); // To hold Number
string Roman; // To hold Roman Numeral
if (Number >= 1 && Number <= 10)
{
switch (Number)
{
case 1:
lblRoman.Text = "I";
break;
case 2:
lblRoman.Text = "II";
break;
case 3:
lblRoman.Text = "III";
break;
case 4:
lblRoman.Text = "IV";
break;
case 5:
lblRoman.Text = "V";
break;
case 6:
lblRoman.Text = "VI";
break;
case 7:
lblRoman.Text = "VII";
break;
case 8:
lblRoman.Text = "VIII";
break;
case 9:
lblRoman.Text = "IX";
break;
case 10:
lblRoman.Text = "X";
break;
}
}
else
{
MessageBox.Show("Error: Invalid Input");
}
}

Instead of switch, You can do other way using Linq which is even better.
int Number=int.Parse(txtNum.Text);
var romanList = new List<string> {"I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX", "X"};
if (Number >= 1 && Number <= 10)
lblRoman.Text = romanList.Select((r, i) => new { Roman = r, Index = i+1}).FirstOrDefault(x=> x.Index == Number).Roman;

you can replace your switch statement this way. and of course you need to assign a variable before using it.
public string GetNum(string val)
{
string res = ""; // Assign it an empty string.
var numToRom = new Dictionary<string, string>
{
{"1","I"},
{"2","II"}
//so on
};
numToRom.TryGetValue(val, out res);
return res;
}

Continuous input to switch case until i press exit c#

I am trying to create a program where the application should never exit until I press option '6'. Below is my sample program: Right now, if I press any option, it executes the corresponding method and console window closes (exits the application) after it is done executing. I want the console to wait for the next option to be entered.
Console.WriteLine(#"Select one of the following option:
1-Write Apps
2-Write Drivers
3-Write OS
4-Write Packages
5-All the above
6-Exit");
string strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
switch (selectionKey)
{
case 1:
DoApps(reqObj);
return;
case 2:
DoDrivers(reqObj);
return;
case 3:
DoOS(reqObj);
return;
case 4:
DoPackages(reqObj);
return;
case 5:
DoAll(reqObj);
return;
case 6:
Environment.Exit(0);
return;
default:
DoAll(reqObj);
return;
}

You can just place your code into a loop, and change the return to break statements:
while(true) // Loop forever
{
string strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
switch (selectionKey)
{
case 1:
DoApps(reqObj);
break; // Break, don't return
case 2:
DoDrivers(reqObj);
break;
case 3:
DoOS(reqObj);
break;
case 4:
DoPackages(reqObj);
break;
case 5:
DoAll(reqObj);
break;
case 6:
Environment.Exit(0);
break;
default:
DoAll(reqObj);
break;
}
}
If you wish to prompt for input each iteration, you can move the prompt into the loop, as well.

using System;
namespace LoopUntilSelectionTester
{
class Program
{
static void Main()
{
string key;
while((key = Console.ReadKey().KeyChar.ToString()) != "6")
{
int keyValue;
int.TryParse(key, out keyValue);
ProcessInput(keyValue);
}
}
private static void ProcessInput(int keyValue)
{
switch (keyValue)
{
case 1:
DoApps(reqObj);
break;
case 2:
DoDrivers(reqObj);
break;
case 3:
DoOS(reqObj);
break;
case 4:
DoPackages(reqObj);
break;
case 5:
DoAll(reqObj);
break;
}
}
}
}

First, what I'd do is make it into a method:
public void AskForInput()
{
Console.WriteLine(#"Select one of the following options:
1-Write Apps
2-Write Drivers
3-Write OS
4-Write Packages
5-All the above
6-Exit");
string strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
switch (selectionKey)
{
case 1:
DoApps(reqObj);
return;
case 2:
DoDrivers(reqObj);
return;
case 3:
DoOS(reqObj);
return;
case 4:
DoPackages(reqObj);
return;
case 5:
DoAll(reqObj);
return;
case 6:
Environment.Exit(0);
return;
default:
DoAll(reqObj);
return;
}
}
and then just use it like this:
for (;;) AskForInput();

Just wrap the whole thing in a while statement.
while (true)
{
Console.WriteLine(#"Select one of the following option:
1-Write Apps
2-Write Drivers
3-Write OS
4-Write Packages
5-All the above
6-Exit");
string strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
switch (selectionKey)
{
case 1:
DoApps(reqObj);
break;
case 2:
DoDrivers(reqObj);
break;
case 3:
DoOS(reqObj);
break;
case 4:
DoPackages(reqObj);
break;
case 5:
DoAll(reqObj);
break;
case 6:
Environment.Exit(0);
break;
default:
DoAll(reqObj);
break;
}
}

This worked for me:
Console.WriteLine(#"Select one of the following option:
1-Write Applications XML
2-Write Drivers XML
3-Write Operating Systems XML
4-Write Packages XML
5-All the above
6-Exit");
string strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
while (true)
{
switch (selectionKey)
{
case 1:
DoApplications(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
case 2:
DoDrivers(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
case 3:
DoOperatingSystems(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
case 4:
DoPackages(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
case 5:
DoAll(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
case 6:
Environment.Exit(0);
break;
default:
DoAll(reqObj);
strReadKey = Console.ReadKey().KeyChar.ToString();
int.TryParse(strReadKey, out selectionKey);
break;
}
}

C#: How can I combine a switch with an if-statement?

I need to combine a switch with an if-statement.
How can I do that? I want to do something like this:
switch (periodtype)
{
if(starttime>endtime)
{
;
}
else
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break;
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}

What's wrong with:
if(starttime<=endtime)
{
switch (periodtype)
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break;
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}

if(starttime>endtime)
{
// Stuff
}
else
{
switch (periodtype)
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}
Like that?

if(starttime>endtime)
{
;
}
else
{
switch (periodtype)
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break;
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}

if(starttime <= endtime)
{
switch (periodtype)
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break;
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}

Hmm way too late with answer
isnt this easier:
if (starttime <= endtime)
{
switch (periodtype)
{
case 0: nextRunTime = nextRunTime.AddHours(period); break;
case 1: nextRunTime = nextRunTime.AddMinutes(period); break;
case 2: nextRunTime = nextRunTime.AddSeconds(period); break;
}
}