DataTable in C# - List type of column and Add method

user_18826471 0
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I created empty DataTable myDT and one of the columns, say Column3 has type List<double>. Now in my code I would like to add sth like this:

myDT.Rows[0]["Column3"].Add(100)

But I can't use Add method here. What can I do instead? I would like to add elements from different pieces of code to the list in a this specific cell.

datatable c#
3 Answers

Because of DataTable.Rows[][] might return object type instance instead of List<double> we need to convert the type as your original type List<double> before call Add method.

In your case, I would use as to try to cast the object to your expected type, if that type is List<double> the list will not be null. make sure our code is safer.

var list = dt.Rows[0]["dd"] as List<double>;
if (list != null)
{
    list.Add(100);
}
user_51760710

If You are using C# 8.0+ version, then you can use is operator with Pattern matching, like

if (dt.Rows[0]["Column3"] is List<double> Column3)
{
    Column3.Add(100);
}
user_62998570

You can use .Field instead.

myDT.Rows[0].Field<List<double>>("Column3").Add(100)
user_48318220
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