used list to loopup for company name but its very slow, any recommedation?

below my code is very slow and has been reported to occasionally throw an exception. wants to know will use of dictionary or ienumerable make any difference?

// Will find the address of the company with the given name.
public string FindAddress(List<Company> companyList, string name)
{
foreach (Company company in companyList)
{
if (name.Trim().ToUpper() == company.Name.ToUpper())
return company.Address;
}

return null;
}

var _cmp=companyList.FirstOrDefault(c=>c.Name.Equals(name, StringComparison.InvariantCultureIgnoreCase));

return (_cmp!=null)?_cmp.Adress:null;