WPF Datagrid Cross row Validation

Question

Does anyone have any example on Cross row validation for WPF Datagrid. Cell level validation and Rowlevel validation doesn't fulfill my requirements. i am trying to stick with MVVM as much as possible. my last option is to use code behind. so basically i need to access the Itemssource when something happens in the grid. any help is much appreciated. Thanks -Rey

Waleed A.K. Waleed A.K. · Accepted Answer · 2010-12-11T22:02:38

on the code behind add a partial class to each table.

The property [HasNoError] is return true if there are no errors

The property [Error] is return the errors as string

if(tablename.HasNoError)
{
// do your logic
}
else
{
// display tablename.Error
}

In the xaml side use the binding

<DataGridTextColumn  Binding="{Binding Path=ActualFieldName1, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged }" Header=" ActualFieldName1"  />

and this is the class sample using IDataErrorInfo-

public partial class tablename : IDataErrorInfo
{
    private Dictionary<string, string> errorCollection = new Dictionary<string, string>();
    public bool HasNoError
    {
        get
        {
            return string.IsNullOrWhiteSpace(Error);
        }
    }
    public string Error
    {
        get
        {
            if (errorCollection.Count == 0)
                return null;
            StringBuilder errorList = new StringBuilder();
            var errorMessages = errorCollection.Values.GetEnumerator();
            while (errorMessages.MoveNext())
                errorList.AppendLine(errorMessages.Current);
            return errorList.ToString();
        }
    }
    public string this[string fieldName]
    {
        get
        {
            string result = null;
            switch (fieldName)
            {
                case "ActualFieldName1":
                    if (string.IsNullOrWhiteSpace(this.ActualFieldName1))
                    {
                        result = "ActualFieldName1 is required.";
                    };
                     if (Other_Condition)
                    {
                        result = "Other Result";
                    };
                    break;
                case "ActualFieldName2":
                    if (string.IsNullOrWhiteSpace(this.ActualFieldName2))
                    {
                        result = "ActualFieldName2 is required.";
                    };
                    if (Other_Condition)
                    {
                        result = "Other Result";
                    };
                    break;
                    // and so
            }
            if (result != null && !errorCollection.ContainsKey(fieldName))
                errorCollection.Add(fieldName, result);
            if (result == null && errorCollection.ContainsKey(fieldName))
                errorCollection.Remove(fieldName);
            return result;
        }
    }
}

To make it nice add some style to target the error template see the example

<Style TargetType="{x:Type TextBox}">
        <Setter Property="Validation.ErrorTemplate">
            <Setter.Value>
                <ControlTemplate>
                    <Border BorderBrush="Red" BorderThickness="1">
                        <Grid>
                            <AdornedElementPlaceholder x:Name="MyAdorner"/>
                            <Image Width="{Binding AdornedElement.ActualHeight, ElementName=MyAdorner}"  Margin="0" ToolTip="{Binding AdornedElement.(Validation.Errors)[0].ErrorContent, ElementName=MyAdorner}" HorizontalAlignment="Right"  VerticalAlignment="Center" Source="/Path/Exclamation.png" />
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

WPF Datagrid Cross row Validation

1 Answers