Find Duplicate entries C#

c#

Solution

LINQ can help you here:

var duplicates = dt.AsEnumerable()
                   .Select(dr => dr.Field<string>("PROV_NEW"))
                   .GroupBy(x => x)
                   .Where(g => g.Count() > 1)
                   .Select(g => g.Key)
                   .ToList();

// Now work with the set of duplicates

Alternatively:

HashSet<string> providers = new HashSet<string>();
foreach (var provider in dt.AsEnumerable()
                           .Select(dr => dr.Field<string>("PROV_NEW")))
{
    if (!providers.Add(provider))
    {
        // This provider is a duplicate
    }
}

(This works because `HashSet<T>.Add` returns false if the value already exists in the set.)

Problem

I am new to programming so this may seem somewhat straightforward, but I cannot seem to figure it out. I am trying to find duplicate values that are in a datatable in one column of the values. Here is what I was trying to do it with. ``` DataRow[] dupresults = dt.Select("PROV_NEW"); TableIssues = string.Empty; DataTable dtTemp = dt.DefaultView.ToTable(true, "NEW_PROV"); if (dupresults.Length == 0) { return true; } else { foreach (DataRow item in dupresults) { Console.WriteLine(item[1]); TableIssues += "Provider Code is not unique for " + item[1].ToString() + ". Revise non-unique codes.\r\n\n\n\n"; } return false; } ``` Alright, but I am also having it search to make sure that there are no empty fields in PROV_NEW too. so I would not know where to put that. I am very new to c#. I just started last week. I am doing side projects for my father's company. ``` private bool ValidateTable(DataSets.Setup.SETUP_MWPROVDataTable dt, out string TableIssues) { try { //NewCode not used for other row DataRow[] result = dt.Select("PROV_NEW = ''"); DataRow[] dupresults = dt.Select("PROV_NEW"); TableIssues = string.Empty; DataTable dtTemp = dt.DefaultView.ToTable(true, "NEW_PROV"); if (dupresults.Length == 0) { return true; } else { var duplicates = dt.AsEnumerable() .Select(dr => dr.Field<string>("PROV_NEW")) .GroupBy(x => x) .Where(g => g.Count() > 1) .Select(g => g.Key) .ToList(); foreach (DataRow item in dupresults) { Console.WriteLine(item[1]); TableIssues += "Provider Code is not unique for " + item[1].ToString() + ". Revise non-unique codes.\r\n\n\n\n"; } return false; } if (result.Length == 0) { //TODO: Add Next Step for validation return true; } else { foreach (DataRow item in result) { Console.WriteLine(item[1]); TableIssues += "Provider code " + item[1].ToString() + " is blank. Add new Provider code for " + item[1].ToString() +".\r\n\n\n"; } return false; } } catch (Exception) { throw; } } } ```

Original source