如何获取数据库中元素的副本？

从前面问题的程序结构来看，您需要从接口继承类StepAndExpRes并实现.Test_CaseICloneableClone()

public class StepAndExpRes : ICloneable
{
    public int Id { get; set; }
    public string Steps { get; set; }
    public string ExpectedResult { get; set; }

    public object Clone()
    {
        StepAndExpRes s = new StepAndExpRes();
        s.ExpectedResult = this.ExpectedResult;
        s.Id = this.Id;
        s.Steps = this.Steps;
        return s;
    }
}

由于它 Test_Case包含List<StepAndExpRes>，让我们添加一个静态类，该类将包含一个克隆列表的方法：

static class Cloner
{
    public static IList<T> Clone<T>(this IList<T> List) where T : ICloneable
    {
        return List.Select(element => (T)element.Clone()).ToList();
    }
}

然后该类Test_Case将如下所示：

public class Test_Case: ICloneable  
{
    public int Id { get; set; }
    public string Identifier { get; set; }
    public string Title { get; set; }
    public string Preconditions { get; set; }
    public List<StepAndExpRes> StepAndExpResults { get; set; }
    public DateTime Date { get; set; }
    public string Comments { get; set; }
    public string Summary { get; set; }
    public bool check { get; set; }

    public object Clone()
    {
        Test_Case t = new Test_Case();
        t.Id = this.Id;
        t.Identifier = this.Identifier;
        t.Title = this.Title;
        t.Preconditions = this.Preconditions;
        t.StepAndExpResults = (List<StepAndExpRes>)Cloner.Clone(this.StepAndExpResults);
        t.Date = this.Date;
        t.Comments = this.Comments;
        t.Summary = this.Summary;
        t.check = this.check;
        return t;
    }
}

用法：

suite.all_test_cases = (List<Test_Case>)Cloner.Clone(db.Test_Cases.ToList());