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// Gendarme.Rules.Performance.UseStringEmpty
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// Sebastien Pouliot <sebastien@ximian.com>
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// Copyright (C) 2006-2008 Novell, Inc (http://www.novell.com)
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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using Gendarme.Framework;
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using Gendarme.Framework.Engines;
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using Gendarme.Framework.Helpers;
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namespace Gendarme.Rules.Performance {
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/// This rule checks for methods that are using the literal <c>""</c> instead of the
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/// <c>String.Empty</c> field. You'll get slighly better performance by using
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/// <c>String.Empty</c>. Note that in some cases, e.g. in a <c>switch/case</c> statement,
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/// you cannot use a field, so <c>""</c> must be used instead of <c>String.Empty</c>.
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/// string s = String.Empty;
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[Problem ("The method uses literal \"\" instead of String.Empty.")]
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[Solution ("Replace the empty string literal with String.Empty.")]
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[EngineDependency (typeof (OpCodeEngine))]
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public class UseStringEmptyRule : Rule, IMethodRule {
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public RuleResult CheckMethod (MethodDefinition method)
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// rule apply only if the method has a body (e.g. p/invokes, icalls don't)
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return RuleResult.DoesNotApply;
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// check if the method loads some string (Ldstr)
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if (!OpCodeEngine.GetBitmask (method).Get (Code.Ldstr))
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return RuleResult.DoesNotApply;
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// *** ok, the rule applies! ***
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// look for string references
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foreach (Instruction ins in method.Body.Instructions) {
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switch (ins.OpCode.OperandType) {
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case OperandType.InlineString:
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string s = (ins.Operand as string);
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Runner.Report (method, ins, Severity.Medium, Confidence.High);
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return Runner.CurrentRuleResult;