Compare a Datatable and string array in c#

问题

I simply want to compare the first col of the datatable called "name" to items in the array. They can be multiple rows in the datatable with the same name. After it has compared all items in the array it should delete the rows that were NOT from the datatable. The output result can be the datatable itself or list array (prefer this) however this should retain all the columns from datatable. Possibly want to use linq query.

code:

DataTable dt = new DataTable("TestTable");
dt.Columns.Add(new DataColumn("email",System.Type.GetType("System.String")));
dt.Columns.Add(new DataColumn("type",System.Type.GetType("System.String")));
dt.Columns.Add(new DataColumn("card",System.Type.GetType("System.String")));

ArrayList al = new ArrayList();
al.Add("one@mail.com");
al.Add("two@mail.com");
al.Add("nine@mail.com");
al.Add("ten@mail.com");

DataRow r1 = dt.NewRow(); r1["email"] = "one@mail.com"; //addtype+card// dt.Rows.Add(r1);

DataRow r2 = dt.NewRow(); r2["email"] = "one@mail.com"; //addtype+card// dt.Rows.Add(r2); 

DataRow r3 = dt.NewRow(); r3["email"] = "two@mail.com"; //addtype+card// dt.Rows.Add(r3);

DataRow r4 = dt.NewRow(); r4["email"] = "four@mail.com"; //addtype+card// dt.Rows.Add(r4);

DataRow r5 = dt.NewRow(); r5["email"] = "five@mail.com"; //addtype+card// dt.Rows.Add(r5);

So from the above row r4 and r5 will be deleted from the datatable.

回答1:

You can do couple of things with your code.

First use List<string> instead of ArrayList (see this for details)
Second add rows to your DataTable, currently you are creating new rows but you are not adding them.

Later with this query you can create a new DataTable which would have rows based on your List of emails.

DataTable dtNew = dt.AsEnumerable()
                   .Where(r => al.Contains(r.Field<string>("email")))
                   .CopyToDataTable();

So your complete code could be:

DataTable dt = new DataTable("TestTable");
dt.Columns.Add(new DataColumn("email", System.Type.GetType("System.String")));
dt.Columns.Add(new DataColumn("type", System.Type.GetType("System.String")));
dt.Columns.Add(new DataColumn("card", System.Type.GetType("System.String")));

List<string> al = new List<string>(); //Use List<string>
al.Add("one@mail.com");
al.Add("two@mail.com");
al.Add("nine@mail.com");
al.Add("ten@mail.com");

DataRow r1 = dt.NewRow(); r1["email"] = "one@mail.com"; //addtype+card// dt.Rows.Add(r1);
dt.Rows.Add(r1);
DataRow r2 = dt.NewRow(); r2["email"] = "one@mail.com"; //addtype+card// dt.Rows.Add(r2); //Add Row to DataTable
dt.Rows.Add(r2);
DataRow r3 = dt.NewRow(); r3["email"] = "two@mail.com"; //addtype+card// dt.Rows.Add(r3);
dt.Rows.Add(r3);
DataRow r4 = dt.NewRow(); r4["email"] = "four@mail.com"; //addtype+card// dt.Rows.Add(r4);
dt.Rows.Add(r4);
DataRow r5 = dt.NewRow(); r5["email"] = "five@mail.com"; //addtype+card// dt.Rows.Add(r5);
dt.Rows.Add(r5);

DataTable dtNew = dt.AsEnumerable()
                   .Where(r => al.Contains(r.Field<string>("email")))
                   .CopyToDataTable();

回答2:

Try

var resultTable = dt.AsEnumberable().Where(r => al.Contains(r.Field<string>("email")).Select(r => r).CopyToDataTable();

来源：https://stackoverflow.com/questions/21529534/compare-a-datatable-and-string-array-in-c-sharp

标签

arrays

linq

datatable