How do I check if my string array exists in my datatable and filter

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C#

<pre> string[] meassteps = { "B1", "B2", "B3", "B4", "B5", "B6", "B7", "B8", "B9", "B10" };

                foreach (string ms in meassteps)
                {
                    conStr = String.Format(conStr, filePath, "Yes");
                    OleDbConnection connExcel = new OleDbConnection(conStr);
                    OleDbCommand cmdExcel = new OleDbCommand();
                    OleDbDataAdapter oda = new OleDbDataAdapter();

                    cmdExcel.Connection = connExcel;

                    DataTable sheets = GetSchemaTable(conStr);
                    connExcel.Open();

                     int cnt = 0;
                     foreach (DataRow r in sheets.Rows)
                         {
                            if (cnt > 0) break;
                            string sheetName = r[2].ToString();

                            DataTable dt = new DataTable(sheetName);


                            cmdExcel.CommandText = "SELECT * From [" + sheetName + "]";
                            oda.SelectCommand = cmdExcel;
                            oda.Fill(dt);

                            dtArray[cnt] = dt;

                            //dt.DefaultView.RowFilter = "measstep";

                            DataRow[] row;
                            row = dt.Select(ms);
                            if (row != null & row.Length > 0)
                            {
                                dt = row.CopyToDataTable();
                                dt = dt.DefaultView.ToTable();

                            }

                }

Hi all. I have a code here which I have created a new string array to search for the meassteps from "B1" to "B10" in my datatable which has a column named "measstep".
What my code is supposed to do is to filter out the measstep and put it in another datatable. If "B1" does not exist in the column "measstep", then search for the next string which is "B2" and filter B2 out and so on, until "B10".

However, I'm having an error that says "Cannot find Column[B1]" when string ms = B1.

How do I write my code such that I'm searching the measstep that is in my datatable?

What I have tried:

I have tried putting my string array into the foreach loop so that the string array exist in my datatable.

Posted 6-May-18 20:21pm

Member 13650651

Updated 6-May-18 21:17pm

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OriginalGriff · Accepted Answer · 2018-05-06T20:37:00

DataTable.Select doesn't work like that: DataTable.Select Method (String) (System.Data)[^] - you are supplying a search criteria thjat is just "B1", or "B2", etc. - which isn't a search. You need to replace that with "ColumnName = 'B1'" and so on.

Quote:
Oh, so I have to replace the string array[] to ColumnName = B1 to B10?

It works like this:

DataTable dt = new DataTable();
dt.Columns.Add("A1");
dt.Columns.Add("A2");
dt.Rows.Add("r1", "B1");
dt.Rows.Add("r2", "B2");
dt.Rows.Add("r3", "B1");
dt.Rows.Add("r4", "B2");
DataRow[] rows = dt.Select("A2 = 'B2'");
foreach (DataRow row in rows)
    {
    Console.WriteLine("{0}:{1}", row[0], row[1]);
    }

Gives:

r2:B2
r4:B2

So I'd change your code like this:

DataRow[] row;
row = dt.Select(string.Format("measstep ='{0}'", ms));

Maciej Los · Accepted Answer · 2018-05-06T21:18:00

First of all: if, you would like to use foreach(...) loop, i'd move few lines of your code outside the foreach(...) loop due to the efficiency. Those are the lines, where you open Excel connection and fill in datatable.
Second of all: you don't need second loop (foreach (DataRow r in sheets.Rows)), because you're using Select method to filter data!

C#

foreach(string ms in meassteps)
{
	DataRow[] msrows= dt.Select(string.Format("measstep Like %{0}%", ms));
}

Another way is to use Linq.
If you would like to filter datatable by comparing each row to the collection of strings, you're able to achieve that by using Where() + Any():

C#

var filteredrows = dt.AsEnumerable()
	.Where(x=> meassteps.Any(y=> x.Field<string>("measstep").Contains(y)))
	.ToList();

or cross join:

C#

var filteredrows1 = from dr in dt.AsEnumerable()
	from ms in meassteps
	where dr.Field<string>("measstep").Contains(ms)
	select dr;

How do I check if my string array exists in my datatable and filter

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