如何读取Xceed DataGrid筛选行中的字符串值？

Great question! I’ve dealt with this exact issue when working with Xceed’s DataGrid, so I know the confusion around the abstract FilterCriterion class. The key here is that FilterCriterion is a base type—different filter operations (equals, contains, range, etc.) have their own concrete implementations that expose the actual filter value. Here’s how to pull out the string representation you need:

Step 1: Check for the FilterCriterion and Handle Concrete Types #

First, you’ll need to check if a filter exists for the column, then cast the FilterCriterion to its specific type to access the value property. Here’s a practical code example:

var collectionView = yourDataGrid.ItemsSource as DataGridCollectionView;
var columnIndex = 0; // Replace with your target column index
var filterCriterion = collectionView.ItemProperties[columnIndex].FilterCriterion;

if (filterCriterion != null)
{
    string filterValue = GetFilterValueAsString(filterCriterion);
    // Use filterValue as needed
    Console.WriteLine($"Filter value for column {columnIndex}: {filterValue}");
}

Step 2: Create a Helper Method for Reusable Logic #

To avoid repeating code (especially for combined filters like AND/OR), extract the logic into a helper method:

private string GetFilterValueAsString(FilterCriterion criterion)
{
    if (criterion == null) return string.Empty;

    // Handle simple filter types
    if (criterion is EqualsFilterCriterion equalsFilter)
        return equalsFilter.Value?.ToString() ?? string.Empty;
    
    if (criterion is ContainsFilterCriterion containsFilter)
        return containsFilter.Value?.ToString() ?? string.Empty;
    
    if (criterion is BetweenFilterCriterion betweenFilter)
        return $"{betweenFilter.MinimumValue?.ToString() ?? "N/A"} - {betweenFilter.MaximumValue?.ToString() ?? "N/A"}";
    
    if (criterion is StartsWithFilterCriterion startsWithFilter)
        return startsWithFilter.Value?.ToString() ?? string.Empty;
    
    if (criterion is EndsWithFilterCriterion endsWithFilter)
        return endsWithFilter.Value?.ToString() ?? string.Empty;

    // Handle combined filters (AND/OR)
    if (criterion is AndFilterCriterion andFilter)
        return string.Join(" AND ", andFilter.Criteria.Select(GetFilterValueAsString).Where(s => !string.IsNullOrEmpty(s)));
    
    if (criterion is OrFilterCriterion orFilter)
        return string.Join(" OR ", orFilter.Criteria.Select(GetFilterValueAsString).Where(s => !string.IsNullOrEmpty(s)));

    // Fallback for unknown filter types
    return criterion.ToString();
}

Key Notes to Keep in Mind #

• Null Safety: Always check if FilterCriterion is null first—if no filter is applied to the column, it will be null.
• Custom Formatting: For non-string data types (dates, numbers), replace ToString() with explicit formatting. For example:

  // Format dates consistently
  equalsFilter.Value?.ToString("yyyy-MM-dd") ?? string.Empty;
  // Format currency
  equalsFilter.Value?.ToString("C2") ?? string.Empty;
  

• Custom Filters: If you’ve implemented custom filter criteria, add additional cases to the helper method to handle those types.

内容的提问来源于stack exchange，提问作者AidanH