WPF datagrid header text binding

Question

The column header of the DataGrid is not a FrameWork element for some reason, and so you cannot use bindings to set things like the header text. Please correct me if that is

Answer 1

My solution allows writing a single line in DataGridColumn with the name of the property that need to bind. He has the following features:

• There is support for DataGridTextColumn
• There is support for DataGridTemplateColumn
• Set StringFormat for each column
• Specify a static value for the StringFormat
• Fully complies with MVVM pattern

Example, which is below, includes StringFormat (he should stand before the PropertyPath):

Equivalent to a this line:

Who need more examples of solutions and features, please read below.

Link for the sample project.

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Notes about the solution

From all the solutions that I have seen earlier, the easiest for me turned out to be this example:

Please pay attention to DataGridTextColumn.HeaderTemplate, if was used DataGridTextColumn.Header, then for .NET framework below version 4.5 and for Silverlight would produce an exception:

Header property does not support UIElements

It would seem that what is necessary? I wanted to find a solution that would allow to write a single line in DataGridColumn with the name of the property that need to bind.

And here's what happened:

This construction similar to this:

Also is possible to use StringFormat for each column like this:

And there is the ability to specify a static value for the StringFormat:

Here is the original DataTemplate, which is dynamically set to the column:

In order to RelativeSource did not depend on the type of DataContext, I took great solution from Mr.Bruno.

In this case, DataGridCellsPanel contains the correct DataContext, which is set for a parent DataGrid.

Below is the basic code that is performed all the magic:

IsSetHeader PropertyChanged handler

private static void IsSetHeader(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
    var textColumn = sender as DataGridTextColumn;
    var templateColumn = sender as DataGridTemplateColumn;
    string path = e.NewValue as string;

    if ((textColumn == null) & (templateColumn == null)) 
    {
        return;
    }

    if (String.IsNullOrEmpty(path) == false)
    {
        currentStringFormat = ReturnStringFormat(textColumn, templateColumn);
        dataTemplate = CreateDynamicDataTemplate(path, currentStringFormat);

        if (dataTemplate != null)
        {
            if (textColumn != null)
                textColumn.HeaderTemplate = dataTemplate;

            if (templateColumn != null)
                templateColumn.HeaderTemplate = dataTemplate;
        }
    }
}

CreateDynamicDataTemplate

private static DataTemplate CreateDynamicDataTemplate(string propertyPath, string stringFormat)
{
    var pc = new ParserContext();
    MemoryStream sr = null;

    string xaml = GetXamlString(propertyPath, stringFormat);            
    sr = new MemoryStream(Encoding.ASCII.GetBytes(xaml));

    pc.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
    pc.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");

    return XamlReader.Load(sr, pc) as DataTemplate;
}

GetXamlString

private static string GetXamlString(string propertyPath, string stringFormat)
{
    #region Original PropertyPath for TextBlock

    // {Binding Path=DataContext.YourProperty, RelativeSource={RelativeSource AncestorType={x:Type DataGridCellsPanel}}}"
    // Thanks to Bruno (https://stackoverflow.com/users/248118/bruno) for this trick

    #endregion

    var sb = new StringBuilder();

    sb.Append("");

    return sb.ToString();
}

StringFormat must appear before the PropertyPath, because it is optional. In order to for columns, who did not have it is not an exception occurs, I registered try-catch in GetStringFormat:

 public static string GetStringFormat(DependencyObject DepObject)
 {
    try
    {
        return (string)DepObject.GetValue(StringFormatProperty);
    }

    catch 
    {
        return String.Empty;
    }
 }

Plus: do not write in methods try-catch block, that are trying to get the value.

Minus: The minus for every missed StringFormat exception will be generated once when the program starts. If it is critical for you, you can always specify the StringFormat="null" for the column.

Just in case, show the full code of project:

public static class DataGridHeader
{
    #region Private Section

    private static string textColumnStringFormat = null;
    private static string templateColumnStringFormat = null;
    private static string currentStringFormat = null;
    private static DataTemplate dataTemplate = null;

    #endregion

    #region PropertyPath DependencyProperty

    public static readonly DependencyProperty PropertyPathProperty;

    public static void SetPropertyPath(DependencyObject DepObject, string value)
    {
        DepObject.SetValue(PropertyPathProperty, value);
    }

    public static string GetPropertyPath(DependencyObject DepObject)
    {
        return (string)DepObject.GetValue(PropertyPathProperty);
    }

    #endregion

    #region StringFormat DependencyProperty

    public static readonly DependencyProperty StringFormatProperty;

    public static void SetStringFormat(DependencyObject DepObject, string value)
    {
        DepObject.SetValue(StringFormatProperty, value);
    }

    public static string GetStringFormat(DependencyObject DepObject)
    {
        try
        {
            return (string)DepObject.GetValue(StringFormatProperty);
        }

        catch 
        {
            return String.Empty;
        }
    }

    #endregion

    #region Constructor

    static DataGridHeader()
    {
        PropertyPathProperty = DependencyProperty.RegisterAttached("PropertyPath",
                                                                   typeof(string),
                                                                   typeof(DataGridHeader),
                                                                   new UIPropertyMetadata(String.Empty, IsSetHeader));

        StringFormatProperty = DependencyProperty.RegisterAttached("StringFormat",
                                                                   typeof(string),
                                                                   typeof(DataGridHeader),
                                                                   new UIPropertyMetadata(String.Empty));  
    }

    #endregion

    #region IsSetHeader PropertyChanged Handler

    private static void IsSetHeader(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        var textColumn = sender as DataGridTextColumn;
        var templateColumn = sender as DataGridTemplateColumn;
        string path = e.NewValue as string;

        if ((textColumn == null) & (templateColumn == null)) 
        {
            return;
        }

        if (String.IsNullOrEmpty(path) == false)
        {
            currentStringFormat = ReturnStringFormat(textColumn, templateColumn);
            dataTemplate = CreateDynamicDataTemplate(path, currentStringFormat);

            if (dataTemplate != null)
            {
                if (textColumn != null)
                    textColumn.HeaderTemplate = dataTemplate;

                if (templateColumn != null)
                    templateColumn.HeaderTemplate = dataTemplate;
            }
        }
    }

    #endregion

    #region ReturnStringFormat Helper

    private static string ReturnStringFormat(DependencyObject depObject1, DependencyObject depObject2) 
    {
        textColumnStringFormat = GetStringFormat(depObject1) as string;
        templateColumnStringFormat = GetStringFormat(depObject2) as string;

        if (String.IsNullOrEmpty(textColumnStringFormat) == false)
        {
            return textColumnStringFormat;
        }

        if (String.IsNullOrEmpty(templateColumnStringFormat) == false)
        {
            return templateColumnStringFormat;
        }

        return "null";
    }

    #endregion

    #region CreateDynamicDataTemplate Helper

    private static DataTemplate CreateDynamicDataTemplate(string propertyPath, string stringFormat)
    {
        var pc = new ParserContext();
        MemoryStream sr = null;

        string xaml = GetXamlString(propertyPath, stringFormat);            
        sr = new MemoryStream(Encoding.ASCII.GetBytes(xaml));

        pc.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
        pc.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");

        return XamlReader.Load(sr, pc) as DataTemplate;
    }

    #endregion

    #region GetXamlString Helper

    private static string GetXamlString(string propertyPath, string stringFormat)
    {
        #region Original PropertyPath for TextBlock

        // {Binding Path=DataContext.YourProperty, RelativeSource={RelativeSource AncestorType={x:Type DataGridCellsPanel}}}"
        // Thanks to Bruno (https://stackoverflow.com/users/248118/bruno) for this trick

        #endregion

        var sb = new StringBuilder();

        sb.Append("");

        return sb.ToString();
    }

    #endregion
}

XAML

Code-behind

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }        

    private void ChangeHeader_Click(object sender, RoutedEventArgs e)
    {
        TestData data = this.DataContext as TestData;

        data.TestStringFormatValue = "777";
        data.TestUsualHeaderValue = "DynamicUsualHeader";
        data.TestTemplateColumnValue = "DynamicTemplateColumn";
    }
}

public class TestData : NotificationObject
{
    #region TestStringFormatValue

    private string _testStringFormatValue = "1";

    public string TestStringFormatValue
    {
        get
        {
            return _testStringFormatValue;
        }

        set
        {
            _testStringFormatValue = value;
            NotifyPropertyChanged("TestStringFormatValue");
        }
    }

    #endregion

    #region TestStaticStringFormatValue

    public static string TestStaticStringFormatValue = "Static StringFormat: {0}$";

    #endregion

    #region TestUsualHeaderValue

    private string _testUsualHeaderValue = "UsualHeader";

    public string TestUsualHeaderValue
    {
        get
        {
            return _testUsualHeaderValue;
        }

        set
        {
            _testUsualHeaderValue = value;
            NotifyPropertyChanged("TestUsualHeaderValue");
        }
    }

    #endregion

    #region TestTemplateColumnValue

    private string _testTemplateColumnValue = "TemplateColumn";

    public string TestTemplateColumnValue
    {
        get
        {
            return _testTemplateColumnValue;
        }

        set
        {
            _testTemplateColumnValue = value;
            NotifyPropertyChanged("TestTemplateColumnValue");
        }
    }

    #endregion
}