Inefficient string.Format or interpolation usage

This article describes performance insights when using Format or string interpolation ($"...").

Cause

Using string.Format or string interpolation frequently results in slow performance.

Performance insight description

Each call to string.Format or string interpolation creates a new string object, resulting in excessive memory allocations and CPU usage when used repeatedly, especially in loops or performance-critical code paths.

If possible, use a StringBuilder for repeated string manipulations, or cache formatted strings when possible. StringBuilder allows for efficient string construction without creating multiple intermediate string objects.

How to investigate a warning

In the CPU Usage tool, click View source code to find where string.Format or string interpolation is used excessively. If possible, refactor to use StringBuilder or minimize formatting operations in hot paths.

See also

StringBuilder documentation