[c#] variables, ifs, simple math and drawing objects

[jayfella]

Here is a little tutorial explains how to declare and use strings and integers, how to perform a basic integrity check and how to make use of these values by using an object. It also shows how to create these objects without using the Design view of Visual Studio.

The code has been commented to make it easier to read, and is fully functional. You can simply copy-paste its entirety into a new project.

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 WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Here we are in the Form_Load function. Everything here is read when the form loads.
            // Right now nothing is being done, so lets assign something:

            // NOTE: we are using a boolean value (true or false) to decide whether to run these functions or not.

            // First declare the absolute size of our form, simply as a confirmation.
            this.Size = new Size(340, 110);

            simpleDeclarations(false); // Execute simpleDeclerations, our first example.

            drawButton(true); // Our second Example
        }

        private void simpleDeclarations(bool executeMe)
        {
            if (!executeMe) return; // if false, just quit right now, else continue.

            // Lets Assign some variables to play with
            string myString;
            int myInt;

            // Notice how we do not have to give either of these a "value" yet.
            // So lets assign them a value now.
            myString = "5";
            myInt = 3;

            // Ok - so lets visibly take a look at the values, just for fun :)
            MessageBox.Show("The Value of myString is: " + myString);
            MessageBox.Show("The Value of myInt is: " + myInt.ToString());

            // Notice that myInt needs to be converted to a string using ".ToString()" if we want to view it.
            // It would work if we didnt, but we are not leaving anything to chance.
            // MessageBoxes only allow string inputs. So thats what we are going to ensure it gets.

            // Ok - so lets play around a little. Lets do some math.
            int myTotal1 = (myInt + Int32.Parse(myString));
            int myTotal2 = (myInt * Int32.Parse(myString));

            // Notice how the string has to be converted to an integer. You can't add a string and an int together, of course.
            // So lets see the output to see if it worked:

            MessageBox.Show("MyTotal1 Value: " + myTotal1.ToString());
            MessageBox.Show("MyTotal1 Value: " + myTotal2.ToString());
            // Again, we are converting the integer to a string. Even if the .NET framework will "assume" this for you,
            // you should always ensure YOU know what your doing. Don't let the computer assume what it thinks you mean.
            // OK! so now we know how to do simple math using strings and integers, and how to convert strings to integers.

            // Converting integers to strings is easier:
            string tempString = myTotal1.ToString();

            // lets get a little more interesting....
            tempString = "hello world. The total cost is: " + myTotal1.ToString();

            // OK - so those are the basics. But we need to do some basic confirmations here. What if some of these variables are empty?
            // the integers and strings we created cannot be "null" - only zero-length for strings, and '0' for integers.

            if (myInt > 0)
                MessageBox.Show("MyInt has a value greater than zero.");
            else
                MessageBox.Show("myInt has a value of zero.");

            // Now, because this if/else statement is so small (a.k.a "one-liners") we dont need to use parenthesis. 
            // More of that later.
            // Lets check the value of our string to make sure its not empty and move on.

            if (tempString.Length == 0)
                MessageBox.Show("the string TemString has a length value of zero, so must be empty");
            else
                MessageBox.Show("the string TemString has a length greater than zero, so must contain data.");

            // Ok - so thats some basic checking.
            // Lets make this a little more interesting!
        }


        private void drawButton(bool executeMe)
        {
            if (!executeMe) return; // if false, just quit right now, else continue.
            
            Button myButton = new Button(); // Declare our new button and give it a unique id "myButton"
            myButton.Name = "button1"; // Give it a name
            myButton.Size = new Size(50, 23); // Set the size in pixels
            myButton.Location = new Point(10, 10); // Set its location
            myButton.Text = "Click Me"; // Set the visible text on the button
            myButton.Click += new EventHandler(letsPlay); // Declare what the button should do when clicked

            this.Controls.Add(myButton); // Finally, draw the button.
        }
        
        private void letsPlay(object sender, EventArgs e)
        {
            // We are going to make a little project here. We are going to draw a progressbar and make it move.#

            ProgressBar myProgressBar = new ProgressBar(); // Declare ur bar and give it a name "myProgressBar".
            myProgressBar.Size = new Size(300, 20); // Set the height/width of myProgressBar.
            myProgressBar.Location = new Point(10, 40); // Set the location of myProgressBar.

            this.Controls.Add(myProgressBar); // Add the control to the current forum (this).

            // OK - so here we have created a new instance of a progressBar, set its size and location and added it to the form.
            // So why do we have to tell the program to draw it, i hear you ask. Well we can configure as many controls as we
            // like - 10, 100, a thousand controls, and then draw them all at the same time - or we can draw them only when needed.
            // For example. Maybe i only want the progressBar to appear when i click a button? Who knows, but the point is
            // you have the CHOICE when to draw it. You will find this VERY useful once you start to rely less on the Designer.

            // So anyway, lets set some properties; the maximum and minimum value of the progressBar, and the current Value:

            myProgressBar.Maximum = 100; //  The maximum value myProgressBar can have.
            myProgressBar.Minimum = 0; // The minumum value myProgressBar can have.
            myProgressBar.Value = 0; // The current position of the progress bar;

            // Ok - so lets have a play with this bar.

            for (int i = 0; i <= 100; i++)
            {
                System.Threading.Thread.Sleep(20); // Pause for 20 hundredths of a second every second (simulate loading)
                myProgressBar.Value = i; // Set the value of the progressBar to the value of i
            }

            // We could also be a little more professional and show/hide visibility by using the property:
            // myProgressBar.Visible = bool;
            // For example, show the progressBar whilst myProgressBar.Value is greater than myProgressBar.Minimum and less than myProgressBar.Maximum
            // else, hide.

            // Notice how the GUI locks up? This is because we are using the parent thread to update the GUI, and since the loop
            // will not finish until the progressBar reaches 100%, the GUI gets locked until the loop finishes.
            // To get around this, we need to use THREADING and DELEGATES.
            // However, now is not the time. Have fun, enjoy!
        }
    }
} 

jayfella Reviewed by jayfella on 17th Jun 2010. [c#] variables, ifs, simple math and drawing objects Here is a little tutorial explains how to declare and use strings and integers, how to perform a basic integrity check and how to make use of these values by using an object. It also shows how to create these objects without using the Design view of Visual Studio. The code has been commented to make it easier to read, and is fully functional. You can simply copy-paste its entirety into a new project. using System; using System.Collections.Generic; using System.ComponentModel; using Rating: 5