# ASP0006: Do not use non-literal sequence numbers
| | Value |
|-|-|
| **Rule ID** |ASP0006|
| **Category** |Usage|
| **Fix is breaking or non-breaking** |Non-breaking|
## Cause
An invocation on a method in <xref:Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder> containing a sequence number that isn't a literal as a parameter.
## Rule description
Blazor's UI diffing algorithm relies on sequence numbers to determine which elements have changed. Computing the sequence number dynamically or using a counter can result in poor diffing performance. Instead, use a literal sequence number that maps to the source code line for the element. For example, the following code produces an error:
```csharp
using Microsoft.AspNetCore.Components.Rendering;
var builder = new RenderTreeBuilder();
var seqNum = 1;
builder.OpenElement(seqNum, ""div"");
builder.CloseElement();
```
## How to fix violations
To fix a violation of this rule, make sure that calls to methods on the <xref:Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder> class that take a sequence number as a parameter use a literal sequence number.
```csharp
using Microsoft.AspNetCore.Components.Rendering;
var builder = new RenderTreeBuilder();
builder.OpenElement(0, ""div"");
builder.CloseElement();
```
## When to suppress warnings
Do ***not*** suppress a warning from this rule. Using a non-literal sequence number can result in performance degradation.