Question

form.myDataTable.Rows[i][2 * cs] = corr;                
form.myDataTable.Rows[i][2 * cs + 1] = "p" + Convert.ToString(col1) 
                                        + " p" + Convert.ToString(col2);

I need to sort 2*cs column by values and also corresponding names in column 2*cs+1.

I am trying like this:

var corrvalues = new Dictionary(); 
correlationvalues["p" + Convert.ToString(col1) 
                      + " p" + Convert.ToString(col2)] = corr;
sortedvalues = correlationvalues.Values.OrderByDescending;

I am not clear how to use orderbydescending, i am new to c#. Thanks for help.

Answer 1

OrderByDescending is a function, not a property. It has one required parameter, which is a function that takes a value in the collection (in your case, correctionvalues.Values) and returns a “key” to use for comparison purposes. If you just want to compare directly on the values themselves, you can pass in an identity lambda function (e.g. x => x).

var corrvalues = new Dictionary(); 
correlationvalues["p" + Convert.ToString(col1) 
                      + " p" + Convert.ToString(col2)] = corr;
sortedvalues = correlationvalues.Values.OrderByDescending(val => val);

If your values are more complex types (such as a Person class) and you want to sort on a particular field (such as Name), then you could pass in something like this:

sorted = personDict.Values.OrderByDescending(person => person.Name);

See http://msdn.microsoft.com/en-us/library/system.linq.enumerable.orderbydescending.aspx for more detail on OrderByDescending.

You can also learn more about lambda expressions (which is useful if you’re new to C#) here: http://msdn.microsoft.com/en-us/library/bb397687.aspx