/// <summary>
/// 逻辑运算（或）
/// </summary>
/// <param name="predicate">条件表达式</param>
public void Or(Expression <Func <T, bool> > predicate)
{
ParameterExpression candidateExpr = Expression.Parameter(typeof(T), "candidate");
ParameterExpressionVisitor parameterVisitor = new ParameterExpressionVisitor(candidateExpr);
Expression left = parameterVisitor.Visit(this._condition.Body);
Expression right = parameterVisitor.Visit(predicate.Body);
BinaryExpression body = Expression.Or(left, right);
this._condition = Expression.Lambda <Func <T, bool> >(body, candidateExpr);
}
//Private
#region # 合并表达式 —— static Expression<TExpression> Merge<TExpression>(...
/// <summary>
/// 合并表达式
/// </summary>
/// <typeparam name="TExpression">表达式类型</typeparam>
/// <param name="left">左表达式</param>
/// <param name="right">右表达式</param>
/// <param name="operator">操作符</param>
/// <returns>Lambda表达式</returns>
private static Expression <TExpression> Merge <TExpression>(Expression <TExpression> left, Expression <TExpression> right, Func <Expression, Expression, Expression> @operator)
{
// zip parameters (map from parameters of right to parameters of left)
IDictionary <ParameterExpression, ParameterExpression> map = left.Parameters
.Select((expression, index) => new { expression, s = right.Parameters[index] })
.ToDictionary(p => p.s, p => p.expression);
// replace parameters in the right lambda expression with the parameters in the left
ParameterExpressionVisitor parameterExpressionVisitor = new ParameterExpressionVisitor(map);
Expression rightBody = parameterExpressionVisitor.Visit(right.Body);
// create a merged lambda expression with parameters from the left expression
return(Expression.Lambda <TExpression>(@operator.Invoke(left.Body, rightBody), left.Parameters));
}
