Why are the CRM function definitions different for me than the codes I see online?

Question

I apologize for my vague question title

I found a code online that suggests a way to create a queryexpression as follows:

 QueryExpression query = new QueryExpression(entity1Name)
    {
        ColumnSet = new ColumnSet(false)
    };

When I tried to do the same in my code, I got an error that the : no constructor exists for QueryExpression that takes 1 argument. However, I can create my queryexpression using this way:

       QueryExpression query = new QueryExpression();
        query.EntityName=entity1Name;
        ColumnSet cset = new ColumnSet();
        cset.AllColumns = false;

This is just an example of many other CRM objects that also behave differently on my side.

Answer 1

QueryExpression class is defined inside the namespace Microsoft.Xrm.Sdk.Query (from Microsoft.Xrm.Sdk.dll) and it has 2 constructors:

public QueryExpression();
public QueryExpression(string entityName);

if you got an error probably you are not referencing the dll included inside the CRM 2011 SDK