[Analyzer Proposal]: Don't use stringBuilder.Append(new string(c, repeatCount)) #117643
Description
Background and motivation
In microsoft/testfx, we have had an occurrence of this pattern (see microsoft/testfx#6013).
This pattern can be replaced by stringBuilder.Append(c, repeatCount) to avoid the allocation of an intermediate string.
API Proposal
A CAxxx rule shipped in .NET SDK (Category=Performance) that suggests the simplified, and more performant overload of StringBuilder.Append
API Usage
Warning on:
builder.Append(new string(c, repeatCount))A codefix is provided to change the above to:
builder.Append(c, repeatCount)Alternative Designs
No response
Risks
No response