我正在使用EF Core,我需要能够对多个列进行搜索,但有时一个项目可能为空。
var myObject = _Context.CurrentTransformers.Where(a =>
a.ID.ToString().Contains(search) ||
a.ADMSKey.Contains(search) ||
a.AccuracyClass.ToString().Contains(search) ||
a.CoreCount.Contains(search) ||
a.PrimaryCurrentRatio.Contains(search) ||
a.SecondaryCurrentRatio.Contains(search) ||
a.EOLXINIVVC.Contains(search));
我知道在以前的版本中我可以使用UseCSharpNullComparisonBehavior
但是我无法在EF Core中找到ContextOptions
。上面的代码抛出的Object引用没有设置为对象错误的实例。
答案 0 :(得分:3)
我将PredicateBuilder
发布的here扩展为包含名为Search<T>
的扩展方法。
你可以这样称呼它;
var myObject = _Context.CurrentTransformers.Search(search);
<强>代码强>
public static class PredicateBuilder
{
public static Expression<Func<T, bool>> True<T>() { return f => true; }
public static Expression<Func<T, bool>> False<T>() { return f => false; }
public static IQueryable<T> Search<T>(this IQueryable<T> self, string keyword)
{
var predicate = False<T>();
var properties = typeof(T).GetTypeInfo().DeclaredProperties;
foreach (var propertyInfo in properties)
{
if (propertyInfo.GetGetMethod().IsVirtual)
continue;
var parameter = Expression.Parameter(typeof(T), "x");
var property = Expression.Property(parameter, propertyInfo);
var propertyAsObject = Expression.Convert(property, typeof(object));
var nullCheck = Expression.NotEqual(propertyAsObject, Expression.Constant(null, typeof(object)));
var propertyAsString = Expression.Call(property, "ToString", null, null);
var keywordExpression = Expression.Constant(keyword);
var contains = Expression.Call(propertyAsString, "Contains", null, keywordExpression);
var lambda = Expression.Lambda(Expression.AndAlso(nullCheck, contains), parameter);
predicate = predicate.Or((Expression<Func<T, bool>>)lambda);
}
return self.Where(predicate);
}
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
{
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>(Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
}
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
{
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
}
}
答案 1 :(得分:0)
我这样做了:
var myObject = _Context.CurrentTransformers.Where(a =>
a.ID.ToString().Contains(search) ||
a.ADMSKey != null && a.ADMSKey.ToLower().Contains(search.ToLower()) ||
a.AccuracyClass != null && a.AccuracyClass.ToString().ToLower().Contains(search.ToLower()) ||
a.CoreCount != null && a.CoreCount.ToLower().Contains(search.ToLower()) ||
a.PrimaryCurrentRatio != null && a.PrimaryCurrentRatio.ToLower().Contains(search.ToLower()) ||
a.SecondaryCurrentRatio != null && a.SecondaryCurrentRatio.ToLower().Contains(search.ToLower()) ||
a.EOLXINIVVC != null && a.EOLXINIVVC.ToLower().Contains(search.ToLower()));
这样可行,但是那个很脏还是可以做到的?