Methodcall with object as return value

Question

2.00/5 (1 vote)

See more:

Hello there,

I'm a bit stuck at my Settings-file management.
I'm fine with reading and writing but I'd like to clean up some code.

I'd really like to read a settings- item and convert it's value to the needed type.

Some example for a better overview:

The current state:

C#

 public class Pref
    {
        public Boolean ShowHiddenItems { get; set; }
    }
private void Form1_Load(object sender, EventArgs e)
        {
            Pref p = new Pref();

            p.ShowHiddenItems = (bool)ReadSubSetting(p.ShowHiddenItems, "show=", "show=true");

        }

private static object ReadSubSetting(object variable, String def, String line)
        {
            if (variable is bool)
            {
                if (line.StartsWith(def))
                {
                    line = line.Substring(def.Length,
                        line.Length -
                        def.Length);

                    bool bDummy;
                    Boolean.TryParse(line, out bDummy);

                    return bDummy;
                }
            }

            /* More conversations coming... */

            /* Some dummy return */
            return false;
        }

My goal:

C#

private void Form1_Load(object sender, EventArgs e)
        {
            Pref p = new Pref();

            p.ShowHiddenItems = ReadSubSetting(p.ShowHiddenItems, "show=", "show=true");

        }

But when trying this, the compiler tells me that he can not convert an object to a bool (which is okay) but the direct casting is not nice looking.

Anyway, is there a way to accomplish my goal this way or even a better way?

Posted 27-Mar-14 4:53am

zokker13

Add a Solution

Comments

[no name] 27-Mar-14 10:57am

You are probably getting that because ShowHiddenItems is defined as a Boolean type.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Maarten Kools · Accepted Answer · 2014-03-27T05:26:00

You could make the method accept a generic type, and do the casting inside the method, for example like this:

C#

private static T ReadSubSetting<T>(T variable, String def, String line)
{
   if (variable is bool)
   {
       if (line.StartsWith(def))
       {
           line = line.Substring(def.Length, line.Length - def.Length);
			   
            System.ComponentModel.TypeConverter converter = System.ComponentModel.TypeDescriptor.GetConverter(typeof(T));
            return (T)converter.ConvertFrom(line);
        }
   }

   /* More conversations coming... */

   /* Some dummy return */
   return default(T);
}

And then you can call it as following:

C#

Pref p = new Pref();
p.ShowHiddenItems = ReadSubSetting(p.ShowHiddenItems, "show=", "show=true");

This is assuming the type of the variable is the same as the return type of the method.

Keith Barrow · Accepted Answer · 2014-03-27T05:28:00

You are going to run into problems with this strategy - ReadSubSetting returns object, but you are setting this to bool.

A generic parser can be made to work like this:

C#

static void Form1_Load(object sender, EventArgs e)
{
    Pref p = new Pref();
    p.ShowHiddenItems = ReadSubSetting<bool>("true");
}

public static T ReadSubSetting<t>(string value)
{
     return (T)TypeDescriptor.GetConverter(typeof(T)).ConvertFromString(value);
}

You can use the above as starting points. If you need to pre-process according to the type, you can use a construct like if(typeof(T)) == typeof(bool))...
Note only works with primative types[^], but you can write a similar method for non-primatives using casting. You might also have problems with strings with my method but you are starting with strings, so no matter.

Methodcall with object as return value

2 solutions

Solution 1

Solution 2

Add your solution here

Preview 0