Clearing Duplicate Column Cell Values from a DataTable

Question

Good day.

Closest post I saw was this post.

I have a datatable with the following info:

ID    COL1    COL2    COL3
10    ABC     Town    Dog
20    AAA     Town    Dog
30    BBB     Town    Cat
40    CCC     City    Cat
50    DDD     City    Pig

I would like to clear out the columns with similar value, so that only the first instance of each remains. The column to filter is user-input, that it can produce:

ID    COL1    COL2    COL3             ID    COL1    COL2    COL3
10    ABC     Town    Dog              10    ABC     Town    Dog
20    AAA             Dog              20    AAA     Town    
30    BBB             Cat      OR      30    BBB     Town    Cat
40    CCC     City    Cat              40    CCC     City    
50    DDD             Pig              50    DDD     City    Pig

So far, I have a working code, but it performs slowly.

    foreach (string strListVal in lstUniqueString)  //contains the unique values
{
        foreach (DataRow drTableTraverse in dt.Rows)  //match the string vs. all rows
        {
            if (drTableTraverse[strColumnName].ToString() == strListVal && bClearedFirst == false)
            {
                bClearedFirst = true;  //flag for the first instance
                continue;  //skip the first instance, then clear the remaining
            }
            else if (drTableTraverse[strColName].ToString() == strListVal)
            {
                drTableTraverse[strColumnName] = "";  
            }
    }
}

Is there an faster way to achieve the same result? Without using linq, if ever.

If duplicate occur then you want to set as empty value (empty string ) ? — Karthick Rajan, Jul 27 '16 at 06:18
Yes, that is correct. The duplicates will be empty string, and the first instance will retain its value — valmanway, Jul 27 '16 at 06:22

score 0 · Answer 1 · answered Jul 27 '16 at 07:13

this seems like a more optimized solution

foreach (string strListVal in lstUniqueString)
{
    for (int i = 0; i < dt.Rows.Count; i++)
    {
        if (dt.Rows[i][strAttribute].ToString().Equals(strListVal) && bClearedFirst == false)
        {
            bClearedFirst = true;
            continue; //should skip first instance
        }
        else if (dt.Rows[i][strAttribute].ToString().Equals(strListVal) && bClearedFirst == true)
        {
            dt.Rows[i][strAttribute] = DBNull.Value;
        }
    }
    bClearedFirst = false;  //reset
}

Clearing Duplicate Column Cell Values from a DataTable

1 Answers1