I'm usually able to solve my problems with about five minutes of searching but this one has taken several days with no results, so I'll try posing the question.
I have a Form whose DataContext is set to a datatable (would prefer LINQ to SQL but I am stuck w/ Sybase which lacks good support for modern entity frameworks.) I have a combo box sourced by another datatable that should update a column on the forms data table but I can't seem to get the binding for SelectedValue to work correctly.
I get a binding error in my Output window which I am unsure how to resolve but it points to the cause of the problem:
System.Windows.Data Error: 40 : BindingExpression path error: 'color' property not found on 'object' ''DataTable' (HashCode=1796783)'. BindingExpression:Path=color; DataItem='DataTable' (HashCode=1796783); target element is 'ComboBox' (Name='cboColor'); target property is 'SelectedValue' (type 'Object')
I've created a sample app that recreates the problem and provide the Xaml and code behind here
Thanks in advance for your help
<Window x:Class="WPFTestBed.ComboTest"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="ComboTest" Height="300" Width="300"
Loaded="OnLoad">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="126*" />
<ColumnDefinition Width="152*" />
</Grid.ColumnDefinitions>
<DataGrid AutoGenerateColumns="False" Height="243" Margin="8,6,0,0" Name="dgList" VerticalAlignment="Top" CanUserAddRows="False" ItemsSource="{Binding}" SelectionChanged="dgList_SelectionChanged">
<DataGrid.Columns>
<DataGridTextColumn Header="Name" IsReadOnly="True" Binding="{Binding Path=name}" Width="*"/>
<DataGridTextColumn Header="Color" IsReadOnly="True" Binding="{Binding Path=color}" Width="Auto"/>
</DataGrid.Columns>
</DataGrid>
<Grid Grid.Column="1" Height="207" HorizontalAlignment="Left" Margin="6,6,0,0" Name="grdSelection" VerticalAlignment="Top" Width="140" DataContext="{Binding}">
<TextBlock Height="23" HorizontalAlignment="Left" Margin="6,6,0,0" Name="textBlock1" Text="{Binding Path=name}" VerticalAlignment="Top" />
<TextBlock Height="23" HorizontalAlignment="Left" Margin="6,27,0,0" Name="textBlock2" Text="{Binding Path=color}" VerticalAlignment="Top" />
<ComboBox Height="23" HorizontalAlignment="Left" Margin="6,56,0,0" Name="cboColor" VerticalAlignment="Top" Width="120"
ItemsSource="{Binding}" DisplayMemberPath="colorName" SelectedValuePath="colorName" SelectedValue="{Binding Path=color}" />
</Grid>
<Button Content="_Save" Grid.Column="1" Height="23" HorizontalAlignment="Right" Margin="0,0,6,12" Name="btnSave" VerticalAlignment="Bottom" Width="75" Click="btnSave_Click" />
</Grid>
Code behind
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Data;
namespace WPFTestBed
{
/// <summary>
/// Interaction logic for ComboTest.xaml
/// </summary>
public partial class ComboTest : Window
{
public ComboTest()
{
InitializeComponent();
}
private DataTable getList()
{
DataTable dt = new DataTable();
DataRow row;
dt.Columns.Add(new DataColumn("name"));
dt.Columns.Add(new DataColumn("color"));
row = dt.NewRow(); row["name"] = "abe"; row["color"] = "Red"; dt.Rows.Add(row);
row = dt.NewRow(); row["name"] = "bob"; row["color"] = "Yellow"; dt.Rows.Add(row);
row = dt.NewRow(); row["name"] = "chuck"; row["color"] = "Blue"; dt.Rows.Add(row);
row = dt.NewRow(); row["name"] = "doug"; row["color"] = "Red"; dt.Rows.Add(row);
row = dt.NewRow(); row["name"] = "eddie"; row["color"] = "Yellow"; dt.Rows.Add(row);
row = dt.NewRow(); row["name"] = "fred"; row["color"] = "Blue"; dt.Rows.Add(row);
return dt;
}
private DataTable getColors()
{
DataTable dt = new DataTable();
DataRow row;
dt.Columns.Add(new DataColumn("colorName"));
row = dt.NewRow(); row["colorName"] = "Red"; dt.Rows.Add(row);
row = dt.NewRow(); row["colorName"] = "Yellow"; dt.Rows.Add(row);
row = dt.NewRow(); row["colorName"] = "Blue"; dt.Rows.Add(row);
return dt;
}
private void OnLoad(object sender, RoutedEventArgs e)
{
dgList.DataContext = getList();
cboColor.DataContext = getColors();
}
private void dgList_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// Get the selected Item
DataRowView selectedRow = (DataRowView)dgList.SelectedCells[0].Item;
//For Illustrative purposes - in "real life" the data table used for the DataContext would come from the database
DataTable dt = new DataTable();
dt.Columns.Add(new DataColumn("name"));
dt.Columns.Add(new DataColumn("color"));
DataRow row = dt.NewRow(); row["name"] = selectedRow["name"].ToString(); row["color"] = selectedRow["color"]; dt.Rows.Add(row);
// Set the data context for the form
grdSelection.DataContext = dt;
}
private void btnSave_Click(object sender, RoutedEventArgs e)
{
DataTable dt = (DataTable)grdSelection.DataContext;
// dt is not updated by combobox binding as expected
}
}
}
