C# 如何将一个数据库表转换为;“支点”;数据表?
我有如下数据,例如:C# 如何将一个数据库表转换为;“支点”;数据表?,c#,mysql,asp.net,linq,datatable,C#,Mysql,Asp.net,Linq,Datatable,我有如下数据,例如: | MemberID | Username | QuestionID | Question | Answer | |----------|----------|------------|------------------|--------| | 58 | John | 1 | Recommend This? | Yes | | 58 | John | 2 | Ho
| MemberID | Username | QuestionID | Question | Answer |
|----------|----------|------------|------------------|--------|
| 58 | John | 1 | Recommend This? | Yes |
| 58 | John | 2 | How much rating? | 10 |
| 59 | Zess | 1 | Recommend This? | No |
| 59 | Zess | 2 | How much rating? | 8 |
有这样一个类(请忽略一些字段):
并使用mysql阅读器将数据添加到报表列表:
while (reader.Read())
{
reportlist.Add(new reportlist() { MemberID = reader["MemberID"].ToString(), Username = reader["Username"].ToString(),
Name = reader["Name"].ToString(), Email = reader["Email"].ToString(), QuestionID = int.Parse(reader["QuestionID"].ToString()), Question = reader["Question"].ToString(),
Answer = reader["Answer"].ToString(), Submitted_On = DateTime.Parse(reader["CreationDate"].ToString()), TotalPoint = int.Parse(reader["TotalPoint"].ToString()) });
}
现在我陷入困境,我尝试使用Linq查询:
var groupedList = reportlist
.GroupBy(u => u.QuestionID, u => u.MemberID)
.ToList();
DataTable dt = new DataTable();
foreach (var group in groupedList)
{
//add columns, rows to datatable, stuck here
}
并且不确定如何将这些结果获取到数据表中。基本上,我想将问题分组,让它成为列,并将所有数据添加到datatable以形成这些结果(示例):
请指导如何获得结果或更好的解决方案?我被困了很长一段时间,因为我在林克表现不好。我确实试着四处搜索,结果不多,可能不太明白它是如何工作的
旁白:最终数据表用于EPPlus库(用于生成excel电子表格)显然,您在问题中发布的代码不能是您的真实代码,因为它具有以下特点,永远不会编译:
class reportlist { ... }
reportlist.Add(new reportlist() { ... });
做出一些假设以回答问题:
List<reportlist> list; // the list filled by the data reader.
使用包含“透视”问题列的数据表设置,我们可以为每个成员获取一行作为值数组:
// Get the column values for each member as an array.
var rows = list
.GroupBy(x => x.MemberID)
.Select(x => {
var memberCols = new object[] { x.Key, x.First().Username };
var answerCols = questions.Select(q => x.Where(a => a.QuestionID == q.Id).Select(a => a.Answer).FirstOrDefault());
return memberCols.Concat(answerCols).ToArray();
});
现在填写表格很容易:
// Fill the table.
foreach (var memberRow in rows)
{
var row = myTable.NewRow().ItemArray = memberRow;
myTable.Rows.Add(row);
}
其中,使用示例数据,代码如下:
// Show the output
for (var i = 0; i < myTable.Columns.Count - 1; i++)
Console.Write("{0}, ", myTable.Columns[i]);
Console.WriteLine("{0}", myTable.Columns[myTable.Columns.Count - 1]);
foreach (var row in myTable.AsEnumerable())
Console.WriteLine(string.Join(", ", row.ItemArray.Select(x => x == null ? "<null>" : x.ToString())));
感谢您的解释和代码。谢谢已经经历了,并且能够解决我的问题。我们一定会学习它,并将其应用到即将到来的工作中~
// Get the column values for each member as an array.
var rows = list
.GroupBy(x => x.MemberID)
.Select(x => {
var memberCols = new object[] { x.Key, x.First().Username };
var answerCols = questions.Select(q => x.Where(a => a.QuestionID == q.Id).Select(a => a.Answer).FirstOrDefault());
return memberCols.Concat(answerCols).ToArray();
});
// Fill the table.
foreach (var memberRow in rows)
{
var row = myTable.NewRow().ItemArray = memberRow;
myTable.Rows.Add(row);
}
// Show the output
for (var i = 0; i < myTable.Columns.Count - 1; i++)
Console.Write("{0}, ", myTable.Columns[i]);
Console.WriteLine("{0}", myTable.Columns[myTable.Columns.Count - 1]);
foreach (var row in myTable.AsEnumerable())
Console.WriteLine(string.Join(", ", row.ItemArray.Select(x => x == null ? "<null>" : x.ToString())));
Member ID, User Name, Recommend This?, How much rating?
58, John, Yes, 10
59, Zess, No, 8