C# 比较两个数据表并选择第二个表中不存在的行
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Compare two DataTables and select the rows that are not present in second table
提问by Catalin
I have two DataTables and I want to select the rows from the first one which are not present in second one
我有两个数据表，我想从第一个中选择第二个中不存在的行
For example:
例如：
Table A id column 1 data1 2 data2 3 data3 4 data4 Table B id column 1 data10 3 data30
I want the result to be:
我希望结果是：
Table C id column 2 data2 4 data4
采纳答案by Tim Schmelter
You can use Linq, especially Enumerable.Excepthelps to find id's in TableA that are not in TableB:
您可以使用 Linq，尤其Enumerable.Except有助于在 TableA 中查找不在 TableB 中的 ID：
var idsNotInB = TableA.AsEnumerable().Select(r => r.Field<int>("id"))
.Except(TableB.AsEnumerable().Select(r => r.Field<int>("id")));
DataTable TableC = (from row in TableA.AsEnumerable()
join id in idsNotInB
on row.Field<int>("id") equals id
select row).CopyToDataTable();
You can also use Wherebut it'll be less efficient:
您也可以使用，Where但效率会降低：
DataTable TableC = TableA.AsEnumerable()
.Where(ra => !TableB.AsEnumerable()
.Any(rb => rb.Field<int>("id") == ra.Field<int>("id")))
.CopyToDataTable();
回答by sai
I got a solution which works without LINQ:
我得到了一个无需 LINQ 即可工作的解决方案：
public DataTable CompareDataTables(DataTable first, DataTable second)
{
first.TableName = "FirstTable";
second.TableName = "SecondTable";
//Create Empty Table
DataTable table = new DataTable("Difference");
try
{
//Must use a Dataset to make use of a DataRelation object
using (DataSet ds = new DataSet())
{
//Add tables
ds.Tables.AddRange(new DataTable[] { first.Copy(), second.Copy() });
//Get Columns for DataRelation
DataColumn[] firstcolumns = new DataColumn[ds.Tables[0].Columns.Count];
for (int i = 0; i < firstcolumns.Length; i++)
{
firstcolumns[i] = ds.Tables[0].Columns[i];
}
DataColumn[] secondcolumns = new DataColumn[ds.Tables[1].Columns.Count];
for (int i = 0; i < secondcolumns.Length; i++)
{
secondcolumns[i] = ds.Tables[1].Columns[i];
}
//Create DataRelation
DataRelation r = new DataRelation(string.Empty, firstcolumns, secondcolumns, false);
ds.Relations.Add(r);
//Create columns for return table
for (int i = 0; i < first.Columns.Count; i++)
{
table.Columns.Add(first.Columns[i].ColumnName, first.Columns[i].DataType);
}
//If First Row not in Second, Add to return table.
table.BeginLoadData();
foreach (DataRow parentrow in ds.Tables[0].Rows)
{
DataRow[] childrows = parentrow.GetChildRows(r);
if (childrows == null || childrows.Length == 0)
table.LoadDataRow(parentrow.ItemArray, true);
}
table.EndLoadData();
}
}
}
For more Visit http://microsoftdotnetsolutions.blogspot.in/2012/12/compare-two-datatables.html
更多信息请访问http://microsoftdotnetsolutions.blogspot.in/2012/12/compare-two-datatables.html
回答by Abdul
You can use Linq Enumerable.ExceptMethod function to get diffence between two DataTable's Here i use firstDt and secondDt,remember both Dt's have the same structure.
您可以使用 Linq Enumerable.ExceptMethod 函数来获取两个 DataTable 之间的差异这里我使用 firstDt 和 secondDt，记住两个 Dt 具有相同的结构。
var EntriesNotInB = firstDt.AsEnumerable().Select(r => r.Field<string>("abc")).Except(secondDt.AsEnumerable().Select(r => r.Field<string>("abc")));
if (EntriesNotInB.Count() > 0)
{
DataTable dt = (from row in firstDt.AsEnumerable()join id in EntriesNotInB on row.Field<string>("abc") equals id select row).CopyToDataTable();
foreach (DataRow row in dt.Rows)
{
/////Place your code to manipulate on datatable Rows
}
}
To read more on Enumerable.Except Method,Go to http://msdn.microsoft.com/en-us/library/system.linq.enumerable.except(v=vs.110).aspx
要阅读有关 Enumerable.Except 方法的更多信息，请访问http://msdn.microsoft.com/en-us/library/system.linq.enumerable.except(v=vs.110).aspx
and its Done!!!! Happy Coding.........
它完成了！！！！快乐编码........
