检查List C#中是否存在值

Question

我有一个由存储过程填充的DataTable,以及包含该集合的数据表Requests(RequestNumber and Tasks(TaskId).当我通过任务到达第一个请求编号时,我将其添加到我的列表中,然后使用其他数据行,我检查列表以查看它们是否存在(if(dr["RequestNumber"].ToString() != acList[i].RequestNumber))如果有,我删除dataRow,如果不是,我将它们添加到列表.

这在顺序中很好用,但是如果数据行和列表偏离一个,则允许添加行.如果值存在于列表中,还有其他方法可以完成查找.

提前致谢.

foreach (DataRow dRow in dt.Rows)
{
    DataRow dr = dt.NewRow();
    dr["Project"] = dRow["Project"];
    dr["RequestNumber"] = dRow["RequestNumber"];
    dr["RequestId"] = dRow["RequestId"];
    dr["TaskType"] = dRow["TaskType"];
    dr["TaskId"] = dRow["TaskId"];
    dr["TaskStatus"] = dRow["TaskStatus"];
    dr["AssignedTo"] = dRow["AssignedTo"];
    dr["DateDue"] = dRow["DateDue"];


    if (acList.Count == 0)
    {
        acList.Add(new AssignedClass
        {
            Project = dr["Project"].ToString(),
            RequestNumber = dr["RequestNumber"].ToString(),
            RequestId = dr["RequestId"].ToString(),
            TaskType = dr["TaskType"].ToString(),
            TaskId = dr["TaskId"].ToString(),
            TaskStatus = dr["TaskStatus"].ToString(),
            AssignedTo = dr["AssignedTo"].ToString(),
            DateDue = dr["DateDue"].ToString()
        });
    }

    else
    {
        for (int i = 0; i < acList.Count; i++)
        {

        if(dr["RequestNumber"].ToString() != acList[i].RequestNumber)
        {
            acList.Add(new AssignedClass
            {
                Project = dr["Project"].ToString(),
                RequestNumber = dr["RequestNumber"].ToString(),
                RequestId = dr["RequestId"].ToString(),
                TaskType = dr["TaskType"].ToString(),
                TaskId = dr["TaskId"].ToString(),
                TaskStatus = dr["TaskStatus"].ToString(),
                AssignedTo = dr["AssignedTo"].ToString(),
                DateDue = dr["DateDue"].ToString()
            });
        }
        else
        {
            dr.Delete();
        }
      }
    }

Answer 1

使用LINQ,就像检查是否有匹配一样简单:

if ( !acList.Any(a => a.RequestNumber == dr["RequestNumber"].ToString() )
    acList.Add( ... );

此外,似乎在一开始分配代码dRow到dr没有目的.只需dRow在代码的其余部分直接使用即可.而且我认为您不想将其(acList.Count == 0)视为一种特殊情况,因为这只会导致您必须复制逻辑,从而维护相同代码的两个单独副本.因此,如果我正确地理解了一切,这个简化的代码应该完成同样的事情:

foreach (DataRow dRow in dt.Rows)
{
    if ( !acList.Any(a => a.RequestNumber == dRow["RequestNumber"].ToString() )
    {
        acList.Add(new AssignedClass
        {
            Project = dRow["Project"].ToString(),
            RequestNumber = dRow["RequestNumber"].ToString(),
            RequestId = dRow["RequestId"].ToString(),
            TaskType = dRow["TaskType"].ToString(),
            TaskId = dRow["TaskId"].ToString(),
            TaskStatus = dRow["TaskStatus"].ToString(),
            AssignedTo = dRow["AssignedTo"].ToString(),
            DateDue = dRow["DateDue"].ToString()
        });
    }
}