c# - 如何在 LINQ 查询中放置条件 WHERE 子句

Question

我正在尝试在 condition 为真时执行以下操作，我想执行 WHERE 否则不执行。

var condition = true;

var mast = new List<Master>
{
    new Master{Id = 2, Prop1 = "Default", Prop2 = "Data", Prop3 = 11},
    new Master{Id = 3, Prop1 = "Some", Prop2 = "TestData", Prop3 = 11},
    new Master{Id = 4, Prop1 = "Some", Prop2 = "MoreData", Prop3 = 11},
};

var g = mast.Where(w=> condition ? (x => x.Prop1.ToLower() != "default" || x.Prop2.ToLower() != "data") : true = true).ToList();

上面的代码给我错误，

Type of conditional expression cannot be determined because there is no implicit conversion between 'lambda expression' and 'bool'

Answer 1

只需将条件移动到 lambda 中:

var g = mast.Where(w => (condition
    ? (w.Prop1.ToLower() != "default" || w.Prop2.ToLower() != "data")
    : true)
).ToList();