@Mark Sanchez , I make a code example in this link and you could refer to it to call the powershell in c#.
Example:
string datetime= textBox1.Text;
PowerShell ps = PowerShell.Create();
string script = string.Format("(Get-ChildItem d:\\New.txt).CreationTime = '{0}'", datetime);
ps.AddScript(script);
ps.Invoke();
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