/// <summary>
/// Adds another expression filter to original expression using Or operator
/// </summary>
/// <typeparam name="T">Type of object in the main filter</typeparam>
/// <param name="expr1">Main filter expression</param>
/// <param name="expr2">Additional filter expression on the same type of object as the main expression</param>
/// <returns></returns>
public static Expression <Func <T, bool> > Or <T>(
this Expression <Func <T, bool> > expr1,
Expression <Func <T, bool> > expr2
)
{
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);
var right = rightVisitor.Visit(expr2.Body);
return(Expression.Lambda <Func <T, bool> >(Expression.Or(left, right), parameter));
}
/// <summary>
/// Adds another expression filter to original expression using Or operator
/// </summary>
/// <typeparam name="T">Type of object in the main filter</typeparam>
/// <typeparam name="TNav">Type of the navigation property (can be deeply nested)</typeparam>
/// <param name="expr1">Main filter expression</param>
/// <param name="expr2">Filter expression that filters on the navigated property</param>
/// <param name="navigationProperty">Expression to the navigation property (eg e => e.PropA.PropB) </param>
/// <returns></returns>
public static Expression <Func <T, bool> > Or <T, TNav>(
this Expression <Func <T, bool> > expr1,
Expression <Func <TNav, bool> > expr2,
Expression <Func <T, TNav> > navigationProperty
)
{
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var navVisitor = new ReplaceExpressionVisitor(navigationProperty.Parameters[0], parameter);
var nav = navVisitor.Visit(navigationProperty.Body); // Reset the navigation prop expression to start from the shared parameter
var right = Expression.Invoke(expr2, nav); // Create an expression that navigates to the property
return(Expression.Lambda <Func <T, bool> >(Expression.Or(left, right), parameter));
}