Here is if my DataTable
DataTable dt = new DataTable();
dt.Rows.Add(2,Test1,Sample1);
dt.Rows.Add(2,Test2,Sample2);
dt.Rows.Add(4,Test3,Sample3);
dt.Rows.Add(4,Test4,Sample4);
dt.Rows.Add(2,Test5,Sample5);
I want to display a message "Duplicate record exists for class 4"
It's possible by comparing using two loops, but I want optimized code that will return the duplicate record and display a message. The solution may use LINQ.
Assuming that you get a duplicate record when the value of the first column is identical for two or more rows:
var duplicates = dt.AsEnumerable().GroupBy(r => r[0]).Where(gr => gr.Count() > 1);
Here is an example:
DataTable dt = new DataTable();
dt.Columns.Add();
dt.Columns.Add();
dt.Columns.Add();
dt.Rows.Add(1, "Test1", "Sample1");
dt.Rows.Add(2, "Test2", "Sample2");
dt.Rows.Add(3, "Test3", "Sample3");
dt.Rows.Add(4, "Test4", "Sample4");
dt.Rows.Add(5, "Test5", "Sample5");
var duplicates = dt.AsEnumerable().GroupBy(r => r[0]).Where(gr => gr.Count() > 1).ToList();
Console.WriteLine("Duplicate found: {0}", duplicates.Any());
dt.Rows.Add(1, "Test6", "Sample6"); // Duplicate on 1
dt.Rows.Add(1, "Test6", "Sample6"); // Duplicate on 1
dt.Rows.Add(3, "Test6", "Sample6"); // Duplicate on 3
dt.Rows.Add(5, "Test6", "Sample6"); // Duplicate on 5
duplicates = dt.AsEnumerable().GroupBy(r => r[0]).Where(gr => gr.Count() > 1).ToList();
if (duplicates.Any())
Console.WriteLine("Duplicate found for Classes: {0}", String.Join(", ", duplicates.Select(dupl => dupl.Key)));
Console.ReadLine();
You can get Intersect of two LINQ query or Results. Intersect means find common records between two LINQ results.
Here is example for this.
DataSet ds = new DataSet();
DataTable dt = new DataTable();
DataColumn dc;
DataRow dr;
ds.DataSetName = "products";
dt.TableName = "product";
dc = new DataColumn("product_id",long.MaxValue.GetType());
dt.Columns.Add(dc);
dc = new DataColumn("product_name");
dt.Columns.Add(dc);
dr = dt.NewRow();
dr["product_id"] = 1;
dr["product_name"] = "Monitor";
dt.Rows.Add(dr);
dr = dt.NewRow();
dr["product_id"] = 2;
dr["product_name"] = "Mouse";
dt.Rows.Add(dr);
dr = dt.NewRow();
dr["product_id"] = 3;
dr["product_name"] = "KeyBoard";
dt.Rows.Add(dr);
dr = dt.NewRow();
dr["product_id"] = 4;
dr["product_name"] = "LCD";
dt.Rows.Add(dr);
ds.Tables.Add(dt);
IEnumerable<DataRow> objResult1 = from tbl in dt.AsEnumerable()
where tbl.Field<long>(0) >=3
select tbl;
IEnumerable<DataRow> objResult2 = from tbl in ds.Tables[0].AsEnumerable()
let product_name = tbl.Field<string>(1)
where product_name.StartsWith("Key")
|| product_name.StartsWith("Mo")
select tbl;
IEnumerable<DataRow> objUnionResult = objResult1.Intersect(objResult2);
Response.Write("<br/><br/><b>Intersect Query Results</b>");
foreach (DataRow row in objUnionResult)
{
Response.Write(string.Format("<br/>Product ID: {0} , Product Name: {1}", row.Field<long>(0), row.Field<string>(1)));
}
Response.Write("<br/><br/>");
