Tutorial 4: Bulk Parameter Updates

Learn to modify parameters across multiple elements in a single transaction.

Finished Script: 03_Tutorials/RevitAPI_Fundamentals/04_BulkUpdates.cs

What You'll Learn

• Wrapping modifications in transactions
• String manipulation methods
• Batch processing patterns

Safety First

This tutorial modifies your model. Always:

• Test in a sample project
• Use Revit's Undo if needed

Step 1: The Transaction Wrapper

All Revit model changes must be inside a transaction. To run this example, select any element in Revit first:

// Select an element in Revit first
var element = Selection.FirstOrDefault();
if (element == null) return;

Transact("My Modification Name", () =>
{
    // All modifications go here inside the wrapper
    var param = element.LookupParameter("Comments");
    if (param != null && !param.IsReadOnly)
    {
        param.Set("New Value");
    }
});

The transaction name appears in Revit's Undo history.

Step 2: Find a Parameter by Name

Use LookupParameter for custom or shared parameters. Select an element to test this:

var element = Selection.FirstOrDefault();
if (element == null) return;

var param = element.LookupParameter("Comments");

if (param == null)
{
    Println($"Parameter not found on {element.Name}");
    return;
}

if (param.IsReadOnly)
{
    Println($"Parameter is read-only");
    return;
}

Println($"Targeting Parameter: {param.Definition.Name}");

Step 3: String Manipulation

Common string methods:

string text = "Hello World";

text.ToUpper()      // "HELLO WORLD"
text.ToLower()      // "hello world"
text.Replace("World", "Revit")  // "Hello Revit"
"PREFIX-" + text    // "PREFIX-Hello World"
text + "-SUFFIX"    // "Hello World-SUFFIX"

Step 4: Bulk Update Pattern

// Gather your targets cleanly
var elements = new FilteredElementCollector(Doc)
    .OfCategory(BuiltInCategory.OST_Walls)
    .WhereElementIsNotElementType()
    .ToElements();

int successCount = 0;

Transact("Bulk Update Wall Comments", () =>
{
    foreach (var element in elements)
    {
        var param = element.LookupParameter("Comments");
        
        if (param == null || param.IsReadOnly)
            continue;
        
        string current = param.AsString() ?? "";
        string updated = current.ToUpper();
        
        param.Set(updated);
        successCount++;
    }
});

Println($"Successfully updated {successCount} elements");

Step 5: Add User Options

Let users choose the transformation:

public class Params
{
    [Segmented]
    public string Operation { get; set; } = "UPPERCASE";
    public List<string> Operation_Options => new List<string>
    {
        "UPPERCASE",
        "lowercase",
        "Add Prefix",
        "Add Suffix"
    };
    
    public string PrefixText { get; set; } = "REV-";
}

Then apply based on selection:

string current = "Sample Text";
string operation = "Add Prefix"; // e.g., comes from p.Operation
string prefixText = "REV-";      // e.g., comes from p.PrefixText

string newValue = operation switch
{
    "UPPERCASE" => current.ToUpper(),
    "lowercase" => current.ToLower(),
    "Add Prefix" => prefixText + current,
    "Add Suffix" => current + prefixText,
    _ => current
};

Println($"Result: {newValue}");

Try This

1. Add a "Replace Text" option
2. Create a "Clear All" option that sets to empty string
3. Add a preview mode that shows changes without applying them

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Next: Tutorial 5: Types vs Instances ->