Question

基本上我正在做一些工作来填充数据表。然后，一旦我有了数据表，我就会得到我的结果。那么我想要做的是根据这些结果从原始数据表中选择。我下面的代码是失败的，所以任何帮助都会很棒。第二部分我很好奇，是如何返回一个集合来迭代选择

谢谢！

DataTable invoicesDataTable = null;
try
{
    invoicesDataTable = GetInvoiceIds();
}
catch (Exception ex)
{

}

//new work here
var uniqueCountryCustomer = 
    invoicesDataTable
    .AsEnumerable()
    .GroupBy(row => new
        {
            Department = (string)row["Department"], 
            Attorney = (string)row["MatterNumber"], 
            MatterNo = (string)row["CUSTOMERNAME"]
        });

string depart = string.Empty;
string attorn = string.Empty;
string MatNo = string.Empty;
for (int i = 0; i < uniqueCountryCustomer.ToArray().Length; i++)
{
    var results =
        from myRow in invoicesDataTable.AsEnumerable()
        where myRow.Field<string>("Department") == uniqueCountryCustomer.ToArray()[i].ToString() 
            && myRow.Field<string>("MatterNumber") == uniqueCountryCustomer.ToArray()[i].ToString() 
            && myRow.Field<string>("CUSTOMERNAME") == uniqueCountryCustomer.ToArray()[i].ToString()
        select myRow;
    //now do work on each of these rows from the group
}

Answer 1

我不使用数据表...永远，真的。但你不能这样做：

DataTable invoicesDataTable = null;
try
{
    invoicesDataTable = GetInvoiceIds();
}
catch (Exception ex)
{
}

//new work here
var uniqueCountryCustomer = 
    invoicesDataTable
    .AsEnumerable()
    .GroupBy(row => new
    {
        Department = (string)row["Department"], 
        Attorney = (string)row["MatterNumber"], 
        MatterNo = (string)row["CUSTOMERNAME"]
    });

foreach(var customerGroup in uniqueCountryCustomer)
{
    foreach(var row in customerGroup)
    {
        //now do work on each of these rows from the group
    }
}

是否有某些原因需要在分组后再次从表中获取行？

Answer 2

GroupBy有三个部分： 1）选择密钥 2）选择值 3）如何投影键/值

这里有相当不错的例子：https://msdn.microsoft.com/en-us/library/vstudio/bb534493(v=vs.100).aspx

var uniqueCountryCustomer = 
    invoicesDataTable
    .AsEnumerable()
    .GroupBy(Key => new
    {
        Department = (string)row["Department"], 
        Attorney = (string)row["MatterNumber"], 
        MatterNo = (string)row["CUSTOMERNAME"]
    },Vals => new {
        something1 = ...,
        something2 = ...
    },(Key,Vals)=>new {
        Key=Key,
        Sum=vals.Select(v=>v.something1).Sum(),
        //If you need these
        Max=vals.Select(v=>v.something1).Max(),
        Min=vals.Select(v=>v.something1).Min(),
        Vals=Vals
    });

foreach(var customer in uniqueCountryCustomer)
{
     ... Do stuff ...
     Console.Writeline("Customer {0} owes us a total of {1}",customer.Key.MatterNo,customer.Sum);
     foreach(var things in customer)
     {
        Console.Writeline("...Bill:{0}",var.something1);
     }
}

Answer 3

我认为这段代码失败了：

var results =
    from myRow in invoicesDataTable.AsEnumerable()
    where myRow.Field<string>("Department") == uniqueCountryCustomer.ToArray()[i].ToString() 
        && myRow.Field<string>("MatterNumber") == uniqueCountryCustomer.ToArray()[i].ToString() 
        && myRow.Field<string>("CUSTOMERNAME") == uniqueCountryCustomer.ToArray()[i].ToString()
    select myRow;

您将每个字段与可能不正确的相同值进行比较。

也许您可以将ToString()替换为Department，依此类推？您在GroupBy表达式中使用的那些值？！

分组依据然后根据这些组值进行选择

3 个答案: