Textboks kun indeholdende tal

CSharp kode 

 public Form1()
 {
     InitializeComponent();
     NumberBox.KeyPress += new KeyPressEventHandler(NumberBox_KeyPress);
     NumberBox.Leave += new EventHandler(NumberBox_Leave);
 }
 
 void NumberBox_Leave(object sender, EventArgs e)
 {
     NumberBox.Text = string.Format("{0:N2}", double.Parse(NumberBox.Text));
 }
 
 void NumberBox_KeyPress(object sender, KeyPressEventArgs e)
 {
     if (e.KeyChar != (char)Keys.Back)
     {
         if (!Char.IsDigit(e.KeyChar) && e.KeyChar != '.' && e.KeyChar != ',')
             e.Handled = true;
     }
 }

CSharp kode 

 public Form1()
         {
             InitializeComponent();
 
             textBox1.KeyPress +=new KeyPressEventHandler(CheckText);
         }
 
         private void CheckText(object sender, KeyPressEventArgs e)
         {
             e.Handled = true;                           //For at override standard handling
             char c = e.KeyChar;
             bool ok = false;
             TextBox box = (TextBox) sender;
 
             try
             {
                 Convert.ToInt32("" + c);                //""+c for at lave char'en om til en streng, da vi ellers ender med int uanset indtastning
                 ok = true;
             }
             catch {
                 if (c == ',' && !box.Text.Contains(c))  //Hvis det er en et komma, og der ikke er nogen        
                     ok = true;
             }
 
             if (ok)
             {
                 box.Text += c;
                 box.SelectionStart = box.Text.Length;   //Flytte caret til enden.
             }
         }

CSharp kode 

 public Form1()
         {
             InitializeComponent();
 
             button1.Click += new EventHandler(Clicked);
         }
 
         private void Clicked(object sender, EventArgs e)
         {
             TextBox[] boxes = new TextBox[] { textBox1, textBox2, textBox3 };   //Array med Textboxene hvis der er flere
             int i = 0;                                                          //Tæller så catch{} ved hvad den skal arbejde med
             try
             {
                 while (i < boxes.Length)                                        //Kontroller hver box
                     Convert.ToDouble(boxes[i++].Text);
 
                 //Gør hvad der ellers skulle ske her, bliver aldrig kaldt hvis der opstår fejl
             }
             catch
             {
                 boxes[i].BackColor = Color.Red;
             }
         }

CSharp kode 

 public Form1()
         {
             InitializeComponent();
 
             textBox1.Leave += new EventHandler(FormaterText);
         }
 
         
 
         private void FormaterText(object sender, EventArgs e)
         {
             try
             {
                 TextBox box = (TextBox)sender;
                 box.Text = string.Format("{0:N2}", Convert.ToDouble(box.Text));  //N2 fortæller at det skal formateres XXX.XXX,XX, hvor 2 er antallet er tegn efter decimal tegn
             }
             catch { }
         }

CSharp kode 

 public partial class Form1 : Form
 {
     public Form1()
     {
         InitializeComponent();
 
         XBox.KeyPress += new KeyPressEventHandler(XYBox_KeyPress);
         XBox.Leave += new EventHandler(XYBox_Leave);
 
         YBox.KeyPress += new KeyPressEventHandler(XYBox_KeyPress);
         YBox.Leave += new EventHandler(XYBox_Leave);
 
         ResultBox.Enter += new EventHandler(ResultBox_Enter);
     }
 
     void ResultBox_Enter(object sender, EventArgs e)
     {
         const string msg = "Please enter a value in the {0} field";
 
         if (XBox.Text == string.Empty)
         {
             MessageBox.Show(string.Format(msg, "X"));
             ActiveControl = XBox;
         }
         else if (YBox.Text == string.Empty)
         {
             MessageBox.Show(string.Format(msg, "Y"));
             ActiveControl = YBox;
         }
         else
         {
             var result = double.Parse(XBox.Text) + double.Parse(YBox.Text);
             ResultBox.Text = result.AsDecimalString();
         }
     }
 
     void XYBox_Leave(object sender, EventArgs e)
     {
         var box = (TextBox)sender;
 
         if(!string.IsNullOrWhiteSpace(box.Text))
             box.Text = double.Parse(box.Text).AsDecimalString();
     }
         
     void XYBox_KeyPress(object sender, KeyPressEventArgs e)
     {
         if (e.KeyChar != (char)Keys.Back)
         {
             if (!Char.IsDigit(e.KeyChar) && e.KeyChar != '.' && e.KeyChar != ',')
                 e.Handled = true;
         }
     }
 }

CSharp kode 

 public static class Extensions
 {
     public static string AsDecimalString(this double s)
     {
         return string.Format("{0:N2}", s);
     }
 }