What is the most suitable construct for an object whose database key consists of several columns?

Question

Suppose I have a table in my database consisting of the following columns, 3 of which uniquely identify a row:

CREATE TABLE [dbo].[Lines]
(
    [Attr1] [nvarchar](10) NOT NULL,
    [Attr2] [nvarchar](10) NOT NULL,
    [Attr3] [nvarchar](10) NOT NULL,
    PRIMARY KEY (Attr1, Attr2, Attr3)
)

Now I have an object in my application that represents one of these lines. It contains three properties that correspond to the three Attr columns in the database.

public class Line
{
   public Line(string attr1, string attr2, string attr3) 
   {
        this.Attr1 = attr1;
        this.Attr2 = attr2;
        this.Attr3 = attr3;
   }

   public Attr1 {get; private set;}
   public Attr2 {get; private set;}
   public Attr3 {get; private set;}
}

The application has a second object that stores a collection of these line objects.

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public GetLine(string attr1, string attr2, string attr3)
{
     // return the line from the collection
}

public UpdateLine(Line line)
{
     // update the line in the collection
}

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Answer 1

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Answer 3

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Answer 4

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public Line this[string attr1, string attr2, string attr3] {
   get { 
      // code to find the appropriate line...
   }
}

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Answer 5

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Answer 6

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