How to custom format data in datagridview during databinding

Question

I'm looking a way to format DataGridViewTextBoxColumn so that the value to be databinded is formatted during databind. For example I have a CompanyName property and I need to take first 5 letters from the CompanyName when databinding happens.

I could hook on different DataGridView events (e.g. RowsAdded) and loop through all the rows and do the trick, but I'd like to find more sophisticated way to do this. Since I have decided to use databind, looping through data and modifying it is a bit against the databinding idea.

What I'm after, is how to do same as below, but add your own formatting logic there:

dataGridView1.Columns[colSomeDate.Index].DataPropertyName = "SomeDate";
colSomeDate.DefaultCellStyle.Format = "yyyy";

I think I should implement IFormatProvider, but I don't quite understand how I should implement it.

dataGridView1.Columns[companyName.Index].DataPropertyName = "CompanyName";
companyName.DefaultCellStyle.FormatProvider = new ShortText(); // ShortText should implement IFormatProvider

Answer 1

Add a property to your class that does the substringing for you, and bind to that.

Answer 2

You could always call a custom format function like so from your aspx page:

<asp:GridView ID="gvPlatforms" runat="server" AutoGenerateColumns="false"
          GridLines="None">
<Columns>
    <asp:TemplateField HeaderText="Icon">
        <ItemTemplate>
            <asp:Image ID="imgPlatformLogo" runat="server" ImageUrl='<%#GetImagePath(Eval("Abbr")) %>' />
        </ItemTemplate>
    </asp:TemplateField>
</Columns>

And then in your code behind for that page:

protected string GetImagePath(object abbr){
return string.Format("{0}{1}.gif", Constants.URLs.PLATFORM_LOGOS, abbr.ToString());}

Answer 3

I don't know about the IFormatProvider, but can the DataGridViews CellFormatting-event help you?

private void dataGridView1_CellFormatting(object sender,
    DataGridViewCellFormattingEventArgs e)
{
    if (e.ColumnIndex == 0)
    {
        e.Value = e.Value.ToString().Substring(0, 5); // apply formating here
        e.FormattingApplied = true;
    }
}

http://msdn.microsoft.com/en-us/library/z1cc356h.aspx?ppud=4

Answer 4

This is a code snippet I use for an example of implementing IFormattable and ICustomFormatter.

Implements IFormattable
Implements ICustomFormatter

Public Function Format(ByVal formatExpression As String, ByVal arg As Object, ByVal formatProvider As System.IFormatProvider) As String Implements System.ICustomFormatter.Format
    'type is currently ignored
    '   if type is international then "USPS" should result in international address
    '   if type is international then "US" should result in international address
    '   and so on
    '

    '.NET Framework Class Library
    'IFormattable Interface
    'Remarks - A class that implements IFormattable must support the "G" (general) formatting code. Besides the "G" code, the class can define the list of formatting codes that it supports.

    'is G and g the same?
    '   yes for numeric
    '   no for date/time

    'Standard Numeric Format Strings
    '   G or g - both are the same
    'Standard DateTime Format Strings
    '   g - General date/time pattern (short time)
    '   G - General date/time pattern (long time)


    If Len(formatExpression) = 0 Then
        Return String.Format("{0}", arg)
    End If

    'usps - standardized
    'us - address less country
    'international - all address lines

    If formatExpression.Equals("g") Then
        'general formatting code
        '   as per documentation
        Return GatherAddress(_line1, _line2, _city, _state, _zip, _country, _type, AddressFormat.StandardUS)

    ElseIf formatExpression.Equals("G") Then
        'general formatting code
        '   as per documentation
        Return GatherAddress(_line1, _line2, _city, _state, _zip, _country, _type, AddressFormat.Standardized)

    ElseIf formatExpression.ToUpper.Equals("USPS") Then
        Return GatherAddress(_line1, _line2, _city, _state, _zip, _country, _type, AddressFormat.Standardized)

    ElseIf formatExpression.ToUpper.Equals("US") Then
        Return GatherAddress(_line1, _line2, _city, _state, _zip, _country, _type, AddressFormat.StandardUS)

    ElseIf formatExpression.ToUpper.Equals("INTERNATIONAL") Then
        Return GatherAddress(_line1, _line2, _city, _state, _zip, _country, _type, AddressFormat.International)

    Else
        Return MyBase.ToString()

    End If

End Function

Public Overloads Function ToString(ByVal format As String, ByVal formatProvider As System.IFormatProvider) As String Implements System.IFormattable.ToString
    Return Me.Format(format, Nothing, formatProvider)
End Function

Answer 5

Have you tried using an UnboundExpression (from DevExpress) in the XAML code for the data grid view? That would let you execute a script on the XAML level, provided that you could instantiate the data binding within the expression.

Answer 6

I generally use ValueConverters for this sort of behavior.

something like:

<DataGridTextColumn Binding={Binding CompanyName, Converter={StaticResource CompanyNameShortenerConverter}} />

In the control/page's resources node, you'll need to add something like:

<local:CompanyNameConverter x:Key="CompanyNameShortenerConverter" />

CompanyNameShortenerConverter should implement IValueConverter, and you can add the logic to "shorten" the company names passed in in the "Convert" method.

This keeps the formatting/UI logic separate from the business logic (i.e. no need to add a "helper property" that shortens the name).

Answer 7

It sounds like IFormatProvider is exactly what you need. Then you can define different codes for the different formats you want for the different views.

From Codeproject.

public override string ToString()
{
    return ToString("g", null); // Always support "g" as default format.
}

public string ToString(string format)
{
  return ToString(format, null);
}

public string ToString(IFormatProvider formatProvider)
{
  return ToString(null, formatProvider);
}

public string ToString(string format, IFormatProvider formatProvider)
{
  if (format == null) format = "g"; // Set default format, which is always "g".
  // Continue formatting by checking format specifiers and options.
}