How to filter certain DataRows in a Data Table

I have a DataTable like the one above, what is the efficient way to filter the rows

Col1, Col2, Col3, Col4 should be matching with other row(s)

Col5 differs

something like below,

How to extract the rows which differs by the Col5

Thanks

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I think that you may use ToTable(distinct, columns) method of System.Data.DataView. Below is the code sample:

DataView view = new DataView(table);
DataTable distinctValues = view.ToTable(true, "Col1", "Col2" ,"Col3","Col4","Col5");

---

// DataTable dt = new DataTable(); for (int i = 1; i < 6; i++) dt.Columns.Add("Col" + i); 
// foreach (var c in "EEFG") dt.Rows.Add(("A B C D " + c).Split());   // optional to generate the table

dt = dt.Rows.Cast<DataRow>()
    .GroupBy(r => Tuple.Create(r[0], r[1], r[2], r[3]))          // group by the first 4 values in each row (you can replace the numbers with the indexes or names of your columns)
    .SelectMany(g => g.GroupBy(r => r[4], (k, v) => v.First()))  //  group each group by the 5th value, and select the first row in each group, to get the distinct rows
    .CopyToDataTable();                                          // optional to copy the rows to a new DataTable

Debug.Print(string.Join("n", dt.AsEnumerable().Select(r => string.Join("t", r.ItemArray)))); // optional to print the result

如果没有其他列，可以缩短它获取每个组中不同的行：

dt = dt.Rows.Cast<DataRow>().GroupBy(r => Tuple.Create(r[0], r[1], r[2], r[3])) 
    .SelectMany(g => g.Distinct(DataRowComparer.Default)).CopyToDataTable();

---

运行它并查看k和dr值

var groups = dt.AsEnumerable().GroupBy(x => new { col1 = x["col1"], col2 = x["col2"], col3 = x["col3"], col4 = x["col4"] });

foreach (var group in groups)
{
    var k = group.Key;

    foreach (var dr in group)
    {
    }
}

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