Question

I’d like to Join a List and a DataRowCollection,

my Code so far looks like this:

attrList.Join<Attribute, DataRow, string, Attribute>(
    dt.Rows,
    attr => attr.Name,
    dataRow => dataRow[0].ToString(),
    (a, b) => new Attribute(a.Name, a.Value, b[1].ToString()));

attrList is a List of type MyProject.Attribute, which contains a string-Property “Name”, the DataRowCollection comes from a DataTable (duh) and contains 2 Values, Index 0 contains a string that should match the Name-Property of Attribute (which is why I’m using join) and Index 1 contains a 2nd string-value which will be appended to the existing Attribute using an overloaded ctor.

Unfortunately, this does not work.

Error:

[…]List<[…]> does not contain a definition for Join and the best extension method overload […] has some invalid arguments.

I simply can’t find what’s supposed to be wrong here.

Here’s the Constructor of Attribute:

public Attribute(string name, string value, string control)
{
    this.name = name;
    this.value = value;
    this.control = control;
}

Answer 1

DataTable.Rows is not generic i.e. it does not implement IEnumerable<T> so you can’t use it in Linq, try below:

attrList.Join<Attribute, DataRow, string, Attribute>(
            dt.AsEnumerable(),
            attr => attr.Name,
            dataRow => dataRow[0].ToString(),
            (a, b) => new Attribute(a.Name, a.Value, b[1].ToString()));