Devexpress Aspx Onrowinserting Oldvalues

2 min read 01-01-2025

Devexpress Aspx Onrowinserting Oldvalues

Working with the DevExpress ASPxGridView's OnRowInserting event often requires accessing the original values of a row before it's inserted into the database. This isn't directly accessible like in some other grid controls, requiring a slightly different approach. This post will outline how to achieve this, focusing on clear and practical methods.

Understanding the Challenge

The OnRowInserting event fires before the new row is actually added to the data source. Therefore, the standard e.NewValues collection contains the values the user has entered, but there's no readily available e.OldValues collection. We need a workaround to retrieve the original values if needed for comparisons or other operations.

Retrieving "Old Values"

Since there are no "old values" in the traditional sense within the OnRowInserting event, we need to handle this differently. Here are a few strategies, each suitable for specific scenarios:

1. Storing Values Before Editing

The most straightforward method is storing the original row data before the editing process begins. This can be done in several ways:

Client-side JavaScript: You can use JavaScript to capture the row's values when the edit form is initiated. This approach is particularly helpful for complex scenarios or when significant pre-processing is required. This often necessitates using the client-side capabilities of the DevExpress ASPxGridView.
Hidden Fields: Add hidden fields to your grid's edit form. Populate these hidden fields with the original row's values when the edit operation begins. You can then access these values within the OnRowInserting event handler.

2. Retrieving Data from the Database (Less Efficient)

If you don't store the old values beforehand, you can retrieve them from your database using a unique identifier. This approach is generally less efficient because it involves another database call.

Identify the Key: Before inserting a new row, identify the unique key that will represent this row. In many cases, this might be an auto-incrementing ID.
Database Query: Use this key to query the database and retrieve the original data row. Note this only works if the user is editing an existing row; this is not applicable for genuinely new rows.

Example using Hidden Fields

Let's illustrate the hidden field approach. This is typically easier and more performant.

Assume your grid has a column called "ProductName" and you want to track changes to it:

protected void ASPxGridView1_RowInserting(object sender, DevExpress.Web.Data.ASPxDataInsertingEventArgs e) {
    // Access the original ProductName from a hidden field (assuming its ID is hfProductName)
    string originalProductName = ((ASPxTextBox)ASPxGridView1.FindEditFormTemplateControl("hfProductName")).Text; 

    // ... your code to process originalProductName and e.NewValues["ProductName"] ...
    e.Cancel = false; // Or e.Cancel = true to prevent insertion if needed
}

Remember that FindEditFormTemplateControl requires that the hidden field is part of the grid's edit form template. You'll need to add the hidden field to your edit form template and populate it appropriately.

Choosing the Right Approach

The best method depends on your specific application requirements. For complex edits or large datasets, storing the old values client-side or via hidden fields is generally preferred. Retrieving data from the database should be used only if other options are impractical due to performance concerns. Always prioritize efficiency and maintainability in your code.