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Topic: How do I know what has changed?

Sat, 20 Sep 2008 18:44:53 GMT

Topic Description: Hello,

I have a business object that is bound to a form using BindingSource but before I save the changes I need to show the changes made by the user. I think this should be a simple question but I didn't see any sample or tutorial showing how I could do this. I am thinking that may be I should clone the object after I load it so I can compare the two before updating. Or is there a better way?

Ryan

Replies: 3
Last Reply: Sat, 20 Sep 2008 18:44:53 GMT
Reply By: Ryan Aljets

Reply: Re: How do I know what has changed?

Sat, 20 Sep 2008 18:44:53 GMT

Ish,

This is exactly what I needed to do and this is even simpler than what I expected. The solution you have provided works great and I am able to compare any of the objects rather than hard coding the same thing for each seperate class. While looking for this I also saw the IsDirty property and that is very useful as well.

I have couple of suggestions that I'll be posting soon but overall I am super impressed with what your framework can do.

Ryan

Reply: Re: How do I know what has changed?

Fri, 19 Sep 2008 18:09:27 GMT

Hi Ryan,

This is indeed a very simple thing. What you are looking for is available in a property called OriginalValue on each field. Take a look at the following example code and that should help. If still something is unclear please do let us know.

using (Customers customer = new Customers()) 
{ 
    customer.CustomerID.Value = 1; 
    customer.Load(); 
    customer.FirstName.Value = customer.FirstName.Value + " :)"; 
    foreach (IField fld in customer.Fields) 
    {  
        // each field has a property called OriginalValue 
        if (fld.OriginalValue != null) 
        { 
            // compare if both value and original value are not null 
            if (!fld.IsNull && !fld.OriginalValue.IsNull && fld.Value.Equals(fld.OriginalValue.Value)) // You can compare the fld.Value with fld.OriginalValue.Value 
            { 
                MessageBox.Show(fld.GetResultSetName() + " has not changed!"); 
            } 
            // if both are null then there is no change either. 
            else if (fld.IsNull && fld.OriginalValue.IsNull) 
            { 
                MessageBox.Show(fld.GetResultSetName() + " has not changed!"); 
            } 
            else 
            { 
                MessageBox.Show(fld.GetResultSetName() + " has changed"); 
            } 
        } 
        else 
        { 
            MessageBox.Show(fld.GetResultSetName() + " can not be compared since the original value is not available."); 
        } 
    } 
} 
 

The above method is actually reusable, and you can simply create a method and pass it any business object instance to perform such comparison.

You can also get the original value like this:

using (Customers customer = new Customers()) 
{ 
    customer.CustomerID.Value = 1; 
    customer.Load(); 
    customer.FirstName.Value = customer.FirstName.Value + " :)"; 
    bool equals = customer.FirstName.Value.Equals(customer.FirstName.OriginalValue.Value); 
    MessageBox.Show(equals.ToString()); 
} 
 

Thanks,
Ish

Reply: Re: How do I know what has changed?

Thu, 18 Sep 2008 23:19:07 GMT

Business object already performs a concurrency check even without timestamp column so this means object already has this information. Just not sure how to get it...