/// <summary>
/// 创建一个类型实例属性的条件表达式。形如 ： o=>o.PropertyName == value
/// </summary>
/// <param name="objectType">实例类型。</param>
/// <param name="propertyName">属性名称。</param>
/// <param name="condition">条件运算样式。</param>
/// <param name="value">要进行比较的常值。</param>
public static LambdaExpression MakePropertyConditionLambda(Type objectType, string propertyName, ConditionStyle condition, object value)
{
Guard.ArgumentNotNull(objectType, "objectType");
Guard.ArgumentNullOrWhiteSpaceString(propertyName, "propertyName");
PropertyInfo propertyInfo = GetPropertyInfo(objectType, propertyName, BindingFlags.Public | BindingFlags.Instance);
var constant = (Expression)Expression.Constant(value);
if (value != null && !propertyInfo.PropertyType.Equals(value))
{
constant = Expression.Convert(constant, propertyInfo.PropertyType);
}
var parameter = Expression.Parameter(objectType, "o");
var property = Expression.Property(parameter, propertyInfo);
Expression body = null;
switch (condition)
{
case ConditionStyle.GreaterThan:
body = Expression.GreaterThan(property, constant);
break;
case ConditionStyle.GreaterThanOrEqual:
body = Expression.GreaterThanOrEqual(property, constant);
break;
case ConditionStyle.LessThan:
body = Expression.LessThan(property, constant);
break;
case ConditionStyle.LessThanOrEqual:
body = Expression.LessThanOrEqual(property, constant);
break;
case ConditionStyle.NotEquals:
body = Expression.NotEqual(property, constant);
break;
default:
body = Expression.Equal(property, constant);
break;
}
return(Expression.Lambda(body, parameter));
}
/// <summary>
/// 创建一个类型实例属性的条件表达式。
/// </summary>
/// <typeparam name="T">要对属性进行比较的类型。</typeparam>
/// <typeparam name="TProperty">属性类型。</typeparam>
/// <param name="propertyExpression">属性表达式。</param>
/// <param name="condition">条件运算样式。</param>
/// <param name="value">要进行比较的常值。</param>
public static Expression <Func <T, bool> > MakePropertyConditionLambda <T, TProperty>(Expression <Func <T, TProperty> > propertyExpression, ConditionStyle condition, object value)
{
return((Expression <Func <T, bool> >)MakePropertyConditionLambda(typeof(T), propertyExpression.GetMemberName(), condition, value));
}
