How to write a code snippet to generate a method in C#?

Question

I want to write a code snippet which does following thing, like if I have a class let's say MyClass:

   class MyClass
    {
        public int Age { get; set; }
        public string Name { get; set; }
    }

so the snippet should create following method:

 public bool DoUpdate(MyClass myClass)
  {
        bool isUpdated = false;
        if (Age != myClass.Age)
        {
            isUpdated = true;
            Age = myClass.Age;
        }
        if (Name != myClass.Name)
        {
            isUpdated = true;
            Name = myClass.Name;
        }
        return isUpdated;
    }

So the idea is if I call the snippet for any class it should create DoUpdate method and should write all the properties in the way as I have done in the above example.

So I want to know :

Is it possible to do the above ?
If yes how should I start, any guidance ?

What are the requirements? Are you only looking for properties? Do you want static properties as well? — itsme86
– itsme86, Commented Sep 1, 2012 at 18:55
What are the requirements in terms of performance etc? It would be pretty easy to write a reflection based generic bool DoUpdate<T>(this T target, T source), for example - then: no snippets required! — Marc Gravell
– Marc Gravell, Commented Sep 1, 2012 at 18:59

Marc Gravell · Accepted Answer · 2012-09-01 19:06:28Z

1

How about a utility method instead:

public static class MyUtilities
{
    public static bool DoUpdate<T>(
        this T target, T source) where T: class
    {
        if(target == null) throw new ArgumentNullException("target");
        if(source == null) throw new ArgumentNullException("source");

        if(ReferenceEquals(target, source)) return false;
        var props = typeof(T).GetProperties(
            BindingFlags.Public | BindingFlags.Instance);
        bool result = false;
        foreach (var prop in props)
        {
            if (!prop.CanRead || !prop.CanWrite) continue;
            if (prop.GetIndexParameters().Length != 0) continue;

            object oldValue = prop.GetValue(target, null),
                   newValue = prop.GetValue(source, null);
            if (!object.Equals(oldValue, newValue))
            {
                prop.SetValue(target, newValue, null);
                result = true;
            }
        }
        return result;
    }
}

with example usage:

var a = new MyClass { Name = "abc", Age = 21 };
var b = new MyClass { Name = "abc", Age = 21 };
var c = new MyClass { Name = "def", Age = 21 };

Console.WriteLine(a.DoUpdate(b)); // false - the same
Console.WriteLine(a.DoUpdate(c)); // true - different

Console.WriteLine(a.Name); // "def" - updated
Console.WriteLine(a.Age);

Note that this could be optimized hugely if it is going to be used in a tight loop (etc), but doing so requires meta-programming knowledge.

answered Sep 1, 2012 at 19:06

Marc Gravell

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5 Comments

Embedd_0913 Over a year ago

What if I have other types in the MyClass as properties ?

Embedd_0913 Over a year ago

It's very good solution actually but is it also possible to write a snippet to do the same ?

Marc Gravell Over a year ago

@Praveen define "other types"; re snippet - I have no idea

Embedd_0913 Over a year ago

The problem is this method is very slow coz it's using reflection, that's why instance method could be better.

Marc Gravell Over a year ago

@praveen like I mentioned: it could be made faster with meta-programming. Also, slow is relative - it will still be fast enough for most usages.

coolmine · Accepted Answer · 2012-09-01 19:00:13Z

1

Your snippets should be under

C:\Users\CooLMinE\Documents\Visual Studio (version)\Code Snippets\Visual C#\My Code Snippets

The most easy way you be taking an existent snippet and modifying it to avoid reconstructing the layout of the file.

Here's a template you can work with:

<?xml version="1.0" encoding="utf-8" ?>
<CodeSnippets  xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">
    <CodeSnippet Format="1.0.0">
        <Header>
            <Title>snippetTitle</Title>
            <Shortcut>snippetShortcutWhichYouWillUseInVS</Shortcut>
            <Description>descriptionOfTheSnippet</Description>
            <Author>yourname</Author>
            <SnippetTypes>
                <SnippetType>Expansion</SnippetType>
            </SnippetTypes>
        </Header>
        <Snippet>
            <Declarations>
                <Literal>
                </Literal>
                <Literal Editable="false">
                </Literal>
            </Declarations>
            <Code Language="csharp"><![CDATA[yourcodegoeshere]]>
            </Code>
        </Snippet>
    </CodeSnippet>
</CodeSnippets>

This should come in handy when you want it to generate names based on the class name and so on: http://msdn.microsoft.com/en-us/library/ms242312.aspx

answered Sep 1, 2012 at 19:00

coolmine

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1 Comment

Kevin Hogg Over a year ago

I suggested something similar here stackoverflow.com/a/19247785/687441 but only to create an empty method. Typically I'd use the property snippet (prop<tab><tab> or propfull<tab><tab> where <tab> is the tab key on your keyboard) to create the properties, but if it's always the same code you could hardcode the properties as coolmine suggested; not good for reuse though.

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