如何寫查詢在LINQ對於這種情況

Question

DataSet dataSet = new DataSet(); 
DataTable dataTable = new DataTable("dataTable"); 
dataTable.Columns.Add("caller", typeof(String)); 
dataTable.Columns.Add("callee", typeof(String)); 
dataTable.Rows.Add("999", "888",2012-11-06 12:11:30); 
dataTable.Rows.Add("888", "999",2012-05-06 12:06:30); 
dataTable.Rows.Add("888", "999",2010-05-06 06:06:30); 
dataTable.Rows.Add("999", "555",2012-04-06 12:11:30); 
dataTable.Rows.Add("555", "333",2012-01-06 12:11:30); 
dataTable.Rows.Add("555", "999",2012-10-06 12:11:30); 
dataSet.Tables.Add(dataTable); 

var result = dataSet.Tables["dataTable"].Select().Select(dr => 
new 
{ 
    caller1 = StringComparer.CurrentCultureIgnoreCase.Compare(dr["caller"], dr["callee"]) < 0 ? dr["callee"] : dr["caller"], 
    caller2 = StringComparer.CurrentCultureIgnoreCase.Compare(dr["caller"], dr["callee"]) < 0 ? dr["caller"] : dr["callee"] 
}) 

    .GroupBy(drg => new { drg.caller1, drg.caller2 }) 
    .Select(drg => new { drg.Key.caller1, drg.Key.caller2, count = drg.Count() }); 

該查詢給我造成這樣

caller1 caller2 count 
999  888  3 
999  555  2 
555  333  1 

我想補充的最大和最小日期列也是在這個結果集。我怎樣才能做到這一點。 如果有兩個數字的最大和最小日之間只有一個呼叫將是相同的

Answer 1

試試這個：

DataSet dataSet = new DataSet(); 
DataTable dataTable = new DataTable("dataTable"); 
dataTable.Columns.Add("caller", typeof(String)); 
dataTable.Columns.Add("callee", typeof(String)); 
dataTable.Columns.Add("timestamp", typeof(String)); 
dataTable.Rows.Add("999", "888","2012-11-06 12:11:30"); 
dataTable.Rows.Add("888", "999","2012-05-06 12:06:30"); 
dataTable.Rows.Add("888", "999","2010-05-06 06:06:30"); 
dataTable.Rows.Add("999", "555","2012-04-06 12:11:30"); 
dataTable.Rows.Add("555", "333","2012-01-06 12:11:30"); 
dataTable.Rows.Add("555", "999","2012-10-06 12:11:30"); 
dataSet.Tables.Add(dataTable); 

var result = dataSet.Tables["dataTable"].Select().Select(dr => 
    new { 
     caller1 = StringComparer.CurrentCultureIgnoreCase.Compare(dr["caller"], dr["callee"]) < 0 ? dr["callee"] : dr["caller"], 
     caller2 = StringComparer.CurrentCultureIgnoreCase.Compare(dr["caller"], dr["callee"]) < 0 ? dr["caller"] : dr["callee"], 
     timestamp = DateTime.Parse(dr["timestamp"].ToString()) 
    }) 
    .GroupBy(drg => new { drg.caller1, drg.caller2 }) 
    .Select(drg => new { drg.Key.caller1, drg.Key.caller2, count = drg.Count(), max = drg.Max(x=>x.timestamp), min = drg.Min(x=>x.timestamp) }); 

，這將給你

Answer 2

DataSet dataSet = new DataSet(); 
DataTable dataTable = new DataTable("dataTable"); 
dataTable.Columns.Add("caller", typeof(String)); 
dataTable.Columns.Add("callee", typeof(String)); 
dataTable.Columns.Add("date", typeof(DateTime)); 
dataTable.Rows.Add("999", "888", new DateTime(2012, 11, 06, 12, 11, 30)); 
dataTable.Rows.Add("888", "999", new DateTime(2012, 05, 06, 12, 06, 30)); 
dataTable.Rows.Add("888", "999", new DateTime(2010, 05, 06, 06, 06, 30)); 
dataTable.Rows.Add("999", "555", new DateTime(2012, 04, 06, 12, 11, 30)); 
dataTable.Rows.Add("555", "333", new DateTime(2012, 01, 06, 12, 11, 30)); 
dataTable.Rows.Add("555", "999", new DateTime(2012, 10, 06, 12, 11, 30)); 
dataSet.Tables.Add(dataTable); 

var result = 
    dataSet.Tables["dataTable"] 
     .Select() 
     .GroupBy(item => 
      new 
      { 
       caller1 = Int32.Parse(item["caller"].ToString()) > Int32.Parse(item["callee"].ToString()) ? item["caller"] : item["callee"], 
       caller2 = Int32.Parse(item["caller"].ToString()) > Int32.Parse(item["callee"].ToString()) ? item["callee"] : item["caller"] 
      }) 

     .Select(item => 
      new 
      { 
       caller1 = item.Key.caller1, 
       caller2 = item.Key.caller2, 
       count = item.Count(), 
       minDate = item.Min(min => DateTime.Parse(min["date"].ToString())), 
       maxDate = item.Max(max => DateTime.Parse(max["date"].ToString())) 
      });