Convert DataTable to String Array through Extension Method

Question

I know there are plenty of similar threads out there but my requirement is little different. The basic requirement is to convert a DataTable to array of strings. I am able to do that by creating an Extension method to do that work for me.

public static class ExtensionMethods
{
     public static object ToStringArray(this DataTable dt, params object[] columns)
     {
          //if specifically columns are provided then returns item array values for these columns.
          if (columns != null && columns.Length > 0)
          {
              //return dt.AsEnumerable().Select(x => new[] { //here i want to iterate through columns params }).ToArray();
          }
          else
          {
               return dt.AsEnumerable().Select(x => new[] { x.ItemArray }).ToArray();
          }
      }    
}

If I don't provide column names explicitly then it perfectly returns all rows values as strings array.

var dtData = dataTable.ToStringArray();

But what if i provide column names

var dtData = dataTable.ToStringArray("Column1", "Column2", "Column3");

then how can I iterate through columns to get only provided columns values in this chunk of code

if (columns != null && columns.Length > 0)
{
     return dt.AsEnumerable().Select(x => new[] { //here i want to iterate through columns params }).ToArray();
}

I know I can do that by hard coding the column names as follow:

var dtData = dt.AsEnumerable().Select(x => new[] { x["Column1"], x["Column2"], x["Column3"] }).ToArray();

or

var dtData = dt.AsEnumerable().Select(x => new[] { x.Field<string>("Column1"), x.Field<int>("Column2").ToString(), x.Field<string>("Column3") }).ToArray();

How can I get this working in my Extension method and by using param object[] columns values?

Vijay · Accepted Answer · 2017-05-25 09:02:56Z

3

You could do a select on the columns parameter. I have changed the type from object[] to string[] here.

public static class ExtensionMethods
{
    public static object ToStringArray(this DataTable dt, params string[] columns)
    {
        //if specifically columns are provided then returns item array values for these columns.
        if (columns != null && columns.Length > 0)
        {
            return dt.AsEnumerable().Select(x => columns.Select(c => x[c]).ToArray()).ToArray();
        }
        else
        {
            return dt.AsEnumerable().Select(x => new[] { x.ItemArray }).ToArray();
        }
    }
}

edited May 25, 2017 at 9:02

answered May 25, 2017 at 8:24

Vijay

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2 Comments

Pikoh Over a year ago

I would probably add ToArray to the columns.Select part: columns.Select(c => x[c]).ToArray(). Otherwise, a nice answer

mmushtaq Over a year ago

You did it. Thanks you very much buddy. And @Pikoh thank you very much too, Your suggestion made this answer perfect according to my requirement.

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