A simple way to make a textbox which accepts only numbers and a decimal number separator.
First of all we need to declare some properties.
C#
private List<char> ValidCharacters { get; set; }
This property would contain the list of valid characters. We'll set its values later in the constructor of the class.
private byte NumberOfDecimalPlaces { get; set; }
This property would determine the number of places after decimal separator.
private char DecimalSeparator { get; set; }
This property would determine the decimal separator which can be a dot "." or a comma "," in some countries it can be something else.
Lets set the values to these properties. this can be set into the constructor or the form load event.
if (ValidCharacters == null)
{
ValidCharacters = new List<char>(); // Initializes the property.
}
NumberOfDecimalPlaces = 4; // Sets the number of places after the decimal separator.
DecimalSeparator = ',';// Determines the value for decimal separator.
ValidCharacters.AddRange("1234567890"); // Add valid characters into the list.
ValidCharacters.Add(DecimalSeparator); // Adds decimal separator into the valid characters list.
After setting all the properties into the relevant area just paste the code below into the KeyPress event of the textbox.
C#
private void NumericTextBoxKeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)Keys.Back)
return;
var cursorLocation = NumericTextBox.SelectionStart;
if (e.KeyChar == DecimalSeparator && NumericTextBox.Text.Contains(DecimalSeparator))
{
e.Handled = true;
}
else
{
if (!ValidCharacters.Contains(e.KeyChar))
{
e.Handled = true;
}
else
{
if (NumericTextBox.Text.Contains(DecimalSeparator))
{
var locationOfDot = NumericTextBox.Text.IndexOf(DecimalSeparator);
var textLengthAfterDecimal = NumericTextBox.Text.Substring(locationOfDot, NumericTextBox.Text.Length - (locationOfDot + 1)).Length;
if (cursorLocation > locationOfDot)
{
if (textLengthAfterDecimal >= NumberOfDecimalPlaces)
{
e.Handled = true;
}
}
}
}
}
}
VB
Private m_ValidCharacters As List(Of Char)
Private Property ValidCharacters() As List(Of Char)
Get
Return m_ValidCharacters
End Get
Set
m_ValidCharacters = Value
End Set
End Property
Private m_NumberOfDecimalPlaces As Byte
Private Property NumberOfDecimalPlaces() As Byte
Get
Return m_NumberOfDecimalPlaces
End Get
Set
m_NumberOfDecimalPlaces = Value
End Set
End Property
Private m_DecimalSeparator As Char
Private Property DecimalSeparator() As Char
Get
Return m_DecimalSeparator
End Get
Set
m_DecimalSeparator = Value
End Set
End Property
Private Property DecimalSeparator() As Char
Get
Return m_DecimalSeparator
End Get
Set
m_DecimalSeparator = Value
End Set
End Property
If ValidCharacters Is Nothing Then
ValidCharacters = New List(Of Char)()
End If
NumberOfDecimalPlaces = 4 ' Sets the number of places after the decimal separator.
DecimalSeparator = ","C' Determines the value for decimal separator.
ValidCharacters.AddRange("1234567890") ' Add valid characters into the list.
ValidCharacters.Add(DecimalSeparator) ' Adds decimal separator into the valid
VB
Private Sub NumericTextBoxKeyPress(sender As Object, e As KeyPressEventArgs)
If e.KeyChar = CChar(Keys.Back) Then
Return
End If
Dim cursorLocation = NumericTextBox.SelectionStart
If e.KeyChar = DecimalSeparator AndAlso NumericTextBox.Text.Contains(DecimalSeparator) Then
e.Handled = True
Else
If Not ValidCharacters.Contains(e.KeyChar) Then
e.Handled = True
Else
If NumericTextBox.Text.Contains(DecimalSeparator) Then
Dim locationOfDot = NumericTextBox.Text.IndexOf(DecimalSeparator)
Dim textLengthAfterDecimal = NumericTextBox.Text.Substring(locationOfDot, NumericTextBox.Text.Length - (locationOfDot + 1)).Length
If cursorLocation > locationOfDot Then
If textLengthAfterDecimal >= NumberOfDecimalPlaces Then
e.Handled = True
End If
End If
End If
End If
End If
End Sub
Please leave a comment if this helps you.
