GCop504.md

GCop 504

"The number of arguments in {Format / FormatWith} is incorrect."

"Invalid argument reference in {Format / FormatWith}"

Rule description

The string.Format and string.FormatWith methods inject parameters into a string template. The placeholders (such as {0} and {1}) are meant to correspond to the values passed into the method. If they don't match, it's often a programming mistake that can lead to runtime errors.

Example1

var myVar = string.Format("someText someOtherText", myString);

should be 🡻

var myVar = string.Format("someText {0} someOtherText", myString);

Example2

"This is {0} the {1}".FormatWith("not", "greatest", "world");

should be 🡻

"This is {0} the {1}".FormatWith("not", "greatest");