Question

I have the following class

  public class UIControl
  {
    public string FName{ get; set; }
    public HtmlInputCheckBox SelectCheckBox { get; set; }
    public bool OverrideSelect { get; set; }

    //Want to throw an ApplicationExceptioh if developer uses this constructor and passes
    //chkSelect = null
    public UIControl(string sFieldName, HtmlInputCheckBox chkSelect)
    {
      this.FName= sFieldName;
      this.SelectCheckBox = chkSelect;
    }

    public UIControl(string sFieldName, HtmlInputCheckBox chkSelect, bool overrideSelect)
      : this(sFieldName, chkSelect)
    {
      OverrideSelect = overrideSelect;
    }
  }

I want to make sure that the developer uses the first constructor only when chkSelect is not null.

I want to do a:

throw new ApplicationException("Dev is using the incorrect constructor");

Answer 1

You can use a private constructor thus:

public UIControl(string sFieldName, HtmlInputCheckBox chkSelect) 
    : this(sFieldName, chkSelect, false, false)
{      
}    

public UIControl(string sFieldName, HtmlInputCheckBox chkSelect, 
     bool overrideSelect)      
    : this(sFieldName, chkSelect, overrideSelect, true)    
{      
}  

private UIControl(string sFieldName, HtmlInputCheckBox chkSelect, 
   bool overrideSelect, bool allowOverride)      
{      
    if ((!allowOverride) && (chkSelect == null)) 
         throw new ArgumentException(...);
    this.FName= sFieldName;      
    this.SelectCheckBox = chkSelect;    
    OverrideSelect = overrideSelect;    
}  

There are lots of variants, but as a general rule, have less specific constructors calling more specific ones. For example, the following would also work in your case:

public UIControl(string sFieldName, HtmlInputCheckBox chkSelect)    
    : this(sFieldName, chkSelect, false)
{      
   if (chkSelect == null) throw ...
}    

public UIControl(string sFieldName, HtmlInputCheckBox chkSelect, 
     bool overrideSelect)    
{      
    this.FName= sFieldName;      
    this.SelectCheckBox = chkSelect;    
    this.OverrideSelect = overrideSelect;    
}