C# Parameters: When to Use `in`, `ref`, or `out`?

Usage scenarios of in, ref and out parameters in C#

In C#, when passing parameters to a method, you can use the in, ref or out parameter modifiers. ref is similar to in, but out has a different purpose.

out Parameters: Usage scenario

Using the out parameter:

• The initial value of the parameter has nothing to do with the operation of the method.
• Optimize performance by avoiding unnecessary marshaling of data to external processes.
• Make it clear to readers that the initial value will be overwritten.

Example:

<code class="language-C#">string a, b;
person.GetBothNames(out a, out b);</code>

In this example, the GetBothNames method atomically retrieves two values ​​regardless of the initial values ​​of a and b.

ref Parameters: Usage scenario

Using the ref parameter:

• The initial value of the parameter is related to the operation of the method.
• The passed parameters need to be modified.

Example:

<code class="language-C#">string name = textbox.Text;
bool didModify = validator.SuggestValidName(ref name);</code>

In this example, the initial value of name is necessary for validation purposes, and the method may modify it.

Syntax sugar

out Parameters are more than just syntactic sugar. It provides performance benefits, clarifies the intent of the method, and allows passing uninitialized parameters.

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