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只要十步，你就可以应用表达式树来优化动态调用（一）( 六 )

>(body,inputExp,minLengthPExp);return final;Expression CreateDefaultResult(){var okMethod = typeof(ValidateResult).GetMethod(nameof(ValidateResult.Ok));Debug.Assert(okMethod != null, nameof(okMethod) + " != null");var methodCallExpression = Expression.Call(okMethod);var re = Expression.Assign(resultExp, methodCallExpression);/*** final as:* result = ValidateResult.Ok()*/return re;}Expression CreateValidateNameRequiredExpression(){var requireMethod = typeof(X03PropertyValidationTest03).GetMethod(nameof(ValidateStringRequired));var isOkProperty = typeof(ValidateResult).GetProperty(nameof(ValidateResult.IsOk));Debug.Assert(requireMethod != null, nameof(requireMethod) + " != null");Debug.Assert(isOkProperty != null, nameof(isOkProperty) + " != null");var requiredMethodExp = Expression.Call(requireMethod, nameNameExp, namePropExp);var assignExp = Expression.Assign(resultExp, requiredMethodExp);var resultIsOkPropertyExp = Expression.Property(resultExp, isOkProperty);var conditionExp = Expression.IsFalse(resultIsOkPropertyExp);var ifThenExp =Expression.IfThen(conditionExp,Expression.Return(returnLabel, resultExp));var re = Expression.Block(new[] {resultExp},assignExp,ifThenExp);/*** final as:* result = ValidateNameRequired("Name", input.Name);* if (!result.IsOk)* {*return result;* }*/return re;}Expression CreateValidateNameMinLengthExpression(){var minLengthMethod =typeof(X03PropertyValidationTest03).GetMethod(nameof(ValidateStringMinLength));var isOkProperty = typeof(ValidateResult).GetProperty(nameof(ValidateResult.IsOk));Debug.Assert(minLengthMethod != null, nameof(minLengthMethod) + " != null");Debug.Assert(isOkProperty != null, nameof(isOkProperty) + " != null");var requiredMethodExp = Expression.Call(minLengthMethod,nameNameExp,namePropExp,minLengthPExp);var assignExp = Expression.Assign(resultExp, requiredMethodExp);var resultIsOkPropertyExp = Expression.Property(resultExp, isOkProperty);var conditionExp = Expression.IsFalse(resultIsOkPropertyExp);var ifThenExp =Expression.IfThen(conditionExp,Expression.Return(returnLabel, resultExp));var re = Expression.Block(new[] {resultExp},assignExp,ifThenExp);/*** final as:* result = ValidateNameMinLength("Name", input.Name, minLength);* if (!result.IsOk)* {*return result;* }*/return re;}}}catch (Exception e){Console.WriteLine(e);throw;}}[Test]public void Run(){// see code in demo repo}public static ValidateResult Validate(CreateClaptrapInput input){return _func.Invoke(input, 3);}public static ValidateResult ValidateStringRequired(string name, string value){return string.IsNullOrEmpty(value)? ValidateResult.Error($"missing {name}"): ValidateResult.Ok();}public static ValidateResult ValidateStringMinLength(string name, string value, int minLength){return value.Length < minLength? ValidateResult.Error($"Length of {name} should be great than {minLength}"): ValidateResult.Ok();}}}代码要点：

  1. 正如前文所述 ， 我们修改了 ValidateNameRequired， 并重命名为 ValidateStringRequired 。ValidateNameMinLength -> ValidateStringMinLength 。


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