winforms Inheriting Controls NumberBox
Example
Often you will want to have an input box that takes numbers only. Again by deriving from the standard controls this is easily achieved, for example:
using System;
using System.Windows.Forms;
using System.Globalization;
namespace StackOverflowDocumentation
{
public class SONumberBox : SOTextBox
{
private int decPlaces;
private int extraDecPlaces;
private bool perCent;
private bool useThouSep = true;
private string decSep = ".";
private string thouSep = ",";
private double numVal;
public SONumberBox() : base()
{
}
public bool PerCent
{
get
{
return perCent;
}
set
{
perCent = value;
}
}
public double Value
{
get
{
return numVal;
}
set
{
numVal = value;
if (perCent)
{
double test = numVal * 100.0;
this.Text = FormatNumber(test) + "%";
}
else
{
this.Text = FormatNumber(value);
}
}
}
public bool UseThousandSeparator
{
get
{
return useThouSep;
}
set
{
useThouSep = value;
}
}
public int DecimalPlaces
{
get
{
return decPlaces;
}
set
{
decPlaces = value;
}
}
public int ExtraDecimalPlaces
{
get
{
return extraDecPlaces;
}
set
{
extraDecPlaces = value;
}
}
protected override void OnTextChanged(EventArgs e)
{
string newVal = this.Text;
int len = newVal.Length;
if (len == 0)
{
return;
}
bool neg = false;
if (len > 1)
{
if (newVal.Substring(0, 1) == "-")
{
newVal = newVal.Substring(1, len - 1);
len = newVal.Length;
neg = true;
}
}
double val = 1.0;
string endChar = newVal.Substring(newVal.Length - 1);
switch (endChar)
{
case "M":
case "m":
if (len > 1)
{
val = double.Parse(newVal.Substring(0, len - 1)) * 1000000.0;
}
else
{
val *= 1000000.0;
}
if (neg)
{
val = -val;
}
this.Text = FormatNumber(val);
break;
case "T":
case "t":
if (len > 1)
{
val = double.Parse(newVal.Substring(0, len - 1)) * 1000.0;
}
else
{
val *= 1000.0;
}
if (neg)
{
val = -val;
}
this.Text = FormatNumber(val);
break;
}
base.OnTextChanged(e);
}
protected override void OnKeyPress(KeyPressEventArgs e)
{
bool handled = false;
switch (e.KeyChar)
{
case '-':
if (this.Text.Length == 0)
{
break;
}
else if (this.SelectionStart == 0)
{
//negative being inserted first
break;
}
else
{
handled = true;
break;
}
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
case '0':
case (char)Keys.Back:
break;
case 'M':
case 'm':
case 'T':
case 't':
case '%':
//check last pos
int l = this.Text.Length;
int sT = this.SelectionStart;
int sL = this.SelectionLength;
if ((sT + sL) != l)
{
handled = true;
}
break;
default:
string thisChar = e.KeyChar.ToString();
if (thisChar == decSep)
{
char[] txt = this.Text.ToCharArray();
for (int i = 0; i < txt.Length; i++)
{
if (txt[i].ToString() == decSep)
{
handled = true;
break;
}
}
break;
}
else if (thisChar != thouSep)
{
handled = true;
}
break;
}
if (!handled)
{
base.OnKeyPress(e);
}
else
{
e.Handled = true;
}
}
protected override void OnLeave(EventArgs e)
{
string tmp = this.Text;
if (tmp == "")
{
tmp = "0";
numVal = NumberLostFocus(ref tmp);
this.Text = tmp;
}
if (tmp.Substring(tmp.Length - 1) == "%")
{
tmp = tmp.Substring(0, tmp.Length - 1);
numVal = 0.0;
numVal = NumberLostFocus(ref tmp) / 100.0;
double test = numVal * 100.0;
this.Text = FormatNumber(test) + "%";
}
else if (perCent)
{
numVal = NumberLostFocus(ref tmp);
double test = numVal * 100.0;
this.Text = FormatNumber(test) + "%";
}
else
{
numVal = NumberLostFocus(ref tmp);
this.Text = tmp;
}
base.OnLeave(e);
}
private string FormatNumber(double amount)
{
NumberFormatInfo nF = new NumberFormatInfo();
nF.NumberDecimalSeparator = decSep;
nF.NumberGroupSeparator = thouSep;
string decFormat;
if (useThouSep)
{
decFormat = "#,##0";
}
else
{
decFormat = "#0";
}
if (decPlaces > 0)
{
decFormat += ".";
for (int i = 0; i < decPlaces; i++)
{
decFormat += "0";
}
if (extraDecPlaces > 0)
{
for (int i = 0; i < extraDecPlaces; i++)
{
decFormat += "#";
}
}
}
else if (extraDecPlaces > 0)
{
decFormat += ".";
for (int i = 0; i < extraDecPlaces; i++)
{
decFormat += "#";
}
}
return (amount.ToString(decFormat, nF));
}
private double NumberLostFocus(ref string amountBox)
{
if (amountBox.Substring(0, 1) == decSep)
amountBox = "0" + amountBox;
NumberFormatInfo nF = new NumberFormatInfo();
nF.NumberDecimalSeparator = decSep;
nF.NumberGroupSeparator = thouSep;
try
{
double d = 0.0;
int l = amountBox.Length;
if (l > 0)
{
char[] c = amountBox.ToCharArray();
char endChar = c[l - 1];
switch (endChar)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
{
stripNonNumerics(ref amountBox);
d = Double.Parse(amountBox, nF);
break;
}
case 'm':
case 'M':
{
if (amountBox.Length == 1)
d = 1000000.0;
else
{
string s = amountBox.Substring(0, l - 1);
stripNonNumerics(ref s);
d = Double.Parse(s, nF) * 1000000.0;
}
break;
}
case 't':
case 'T':
{
if (amountBox.Length == 1)
d = 1000.0;
else
{
string s = amountBox.Substring(0, l - 1);
stripNonNumerics(ref s);
d = Double.Parse(s, nF) * 1000.0;
}
break;
}
default:
{
//remove offending char
string s = amountBox.Substring(0, l - 1);
if (s.Length > 0)
{
stripNonNumerics(ref s);
d = Double.Parse(s, nF);
}
else
d = 0.0;
break;
}
}
}
amountBox = FormatNumber(d);
return (d);
}
catch (Exception e)
{
//handle exception here;
return 0.0;
}
}
private void stripNonNumerics(ref string amountBox)
{
bool dSFound = false;
char[] tmp = decSep.ToCharArray();
char dS = tmp[0];
string cleanNum = "";
int l = amountBox.Length;
if (l > 0)
{
char[] c = amountBox.ToCharArray();
for (int i = 0; i < l; i++)
{
char b = c[i];
switch (b)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
cleanNum += b;
break;
case '-':
if (i == 0)
cleanNum += b;
break;
default:
if ((b == dS) && (!dSFound))
{
dSFound = true;
cleanNum += b;
}
break;
}
}
}
amountBox = cleanNum;
}
}
As well as restricting input to numbers, this class has a few special features. It exposes a property Value to represent the double value of the number, it formats the text, optionally with thousand separators, and it provides short-hand entry of large numbers: 10M expands on leave to 10,000,000.00 (the number of decimal places being a property). For the sake of brevity, the decimal and thousand separators have been hard-coded. In a production system, these are also user preferences.
