C# IQueryable.CreateEqualExpression方法代码示例

    public override Expression ToLinqExpression( IQueryable queryable, ParameterExpression parameterExpression, string propertyName )
    {
      if( queryable == null )
        throw new ArgumentNullException( "queryable" );

      if( parameterExpression == null )
        throw new ArgumentNullException( "parameterExpression" );

      if( String.IsNullOrEmpty( propertyName ) )
      {
        if( propertyName == null )
          throw new ArgumentNullException( "propertyName" );

        throw new ArgumentException( "PropertyName must not be empty.", "propertyName" );
      }

      return queryable.CreateEqualExpression( parameterExpression, propertyName, this.Value );
    }

    private IQueryable FilterQueryable( IQueryable queryable )
    {
      // Filters a queryable to match this Group's clause.
      // This method does not apply the AutoFilter clauses or the FilterRow clauses.
      // It is the DataGridVirtualizingQueryableCollectionViewGroupRoot's job to do so on the
      // base queryable used as a base for all other queryables.

      if( queryable == null )
        throw new ArgumentNullException( "queryable" );

      int level = this.Level;

      DataGridVirtualizingCollectionViewBase collectionView = this.GetCollectionView();

      ObservableCollection<GroupDescription> groupDescriptions = collectionView.GroupDescriptions;

      Debug.Assert( ( groupDescriptions != null ) && ( level < groupDescriptions.Count ) );

      DataGridGroupDescription groupBy = groupDescriptions[ level ] as DataGridGroupDescription;

      Debug.Assert( groupBy != null );

      ParameterExpression sharedParameterExpression = queryable.CreateParameterExpression();

      Expression expression = queryable.CreateEqualExpression( sharedParameterExpression, groupBy.PropertyName, this.Name );
      return queryable.WhereFilter( sharedParameterExpression, expression );
    }

    private Expression GetAutoFilterValuesExpression( IQueryable queryable, ParameterExpression sharedParameterExpression )
    {
      if( queryable == null )
        throw new ArgumentNullException( "queryable" );

      AutoFilterMode autoFilterMode = m_parentCollectionView.AutoFilterMode;

      if( autoFilterMode == AutoFilterMode.None )
        return null;

      DataGridItemPropertyCollection itemProperties = m_parentCollectionView.ItemProperties;
      int itemPropertiesCount = itemProperties.Count;

      Expression autoFilterValuesExpression = null;

      for( int i = 0; i < itemPropertiesCount; i++ )
      {
        DataGridItemPropertyBase itemProperty = itemProperties[ i ];
        string itemPropertyName = itemProperty.Name;

        IList itemPropertyAutoFilterValues;

        if( m_parentCollectionView.AutoFilterValues.TryGetValue( itemPropertyName, out itemPropertyAutoFilterValues ) )
        {
          int itemPropertyAutoFilterValuesCount = itemPropertyAutoFilterValues.Count;

          if( itemPropertyAutoFilterValuesCount == 0 )
            continue;


          object[] itemPropertyAutoFilterValuesArray = new object[ itemPropertyAutoFilterValuesCount ];
          itemPropertyAutoFilterValues.CopyTo( itemPropertyAutoFilterValuesArray, 0 );

          Expression itemPropertyAutoFilterExpression = queryable.CreateEqualExpression( sharedParameterExpression, itemPropertyName, itemPropertyAutoFilterValuesArray );

          if( autoFilterValuesExpression == null )
          {
            autoFilterValuesExpression = itemPropertyAutoFilterExpression;
          }
          else
          {
            Debug.Assert( ( autoFilterMode == AutoFilterMode.And ) || ( autoFilterMode == AutoFilterMode.Or ) );

            // Merge this DataGridItemProperty AutoFilterExpressions
            if( autoFilterMode == AutoFilterMode.And )
            {
              autoFilterValuesExpression = Expression.And( autoFilterValuesExpression, itemPropertyAutoFilterExpression );
            }
            else
            {
              autoFilterValuesExpression = Expression.Or( autoFilterValuesExpression, itemPropertyAutoFilterExpression );
            }
          }
        }
        // Loop to next DataGridItemProperty.
      }

      return autoFilterValuesExpression;
    }