/// <summary>
/// 指定 FilterKeyValueAction 获取 Lambda 表达式
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="filter"></param>
/// <returns></returns>
public static Expression <Func <TItem, bool> > GetFilterLambda <TItem>(this FilterKeyValueAction filter)
{
Expression <Func <TItem, bool> > ret = t => true;
if (!string.IsNullOrEmpty(filter.FieldKey) && filter.FieldValue != null)
{
var prop = typeof(TItem).GetProperty(filter.FieldKey);
if (prop != null)
{
var p = Expression.Parameter(typeof(TItem));
var fieldExpression = Expression.Property(p, prop);
Expression eq = fieldExpression;
// 可为空类型转化为具体类型
if (prop.PropertyType.IsGenericType &&
prop.PropertyType.GetGenericTypeDefinition() == typeof(Nullable <>))
{
eq = Expression.Convert(fieldExpression, prop.PropertyType.GenericTypeArguments[0]);
}
eq = filter.GetExpression(eq);
ret = Expression.Lambda <Func <TItem, bool> >(eq, p);
}
}
return(ret);
}
/// <summary>
/// 指定 FilterKeyValueAction 获取 Lambda 表达式
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="filter"></param>
/// <returns></returns>
public static Expression <Func <TItem, bool> > GetFilterLambda <TItem>(this FilterKeyValueAction filter)
{
Expression <Func <TItem, bool> > ret = t => true;
if (!string.IsNullOrEmpty(filter.FieldKey) && filter.FieldValue != null)
{
var prop = typeof(TItem).GetProperty(filter.FieldKey);
if (prop != null)
{
var p = Expression.Parameter(typeof(TItem));
var fieldExpression = Expression.Property(p, prop);
// 可为空类型转化为具体类型
var eq = filter.GetExpression(Expression.Convert(fieldExpression, filter.FieldValue.GetType()));
ret = Expression.Lambda <Func <TItem, bool> >(eq, p);
}
}
return(ret);
}
/// <summary>
/// 指定 FilterKeyValueAction 获取 Lambda 表达式
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="filter"></param>
/// <returns></returns>
public static Expression <Func <TItem, bool> > GetFilterLambda <TItem>(this FilterKeyValueAction filter)
{
Expression <Func <TItem, bool> > ret = t => true;
var type = typeof(TItem);
if (!string.IsNullOrEmpty(filter.FieldKey) && filter.FieldValue != null)
{
ret = filter.FieldKey.Contains(".") ? GetComplexFilterExpression() : GetSimpleFilterExpression();
}
return(ret);
Expression <Func <TItem, bool> > GetSimpleFilterExpression()
{
var prop = typeof(TItem).GetPropertyByName(filter.FieldKey) ?? throw new InvalidOperationException($"the model {type.Name} not found the property {filter.FieldKey}");;
if (prop != null)
{
var p = Expression.Parameter(type);
var fieldExpression = Expression.Property(p, prop);
Expression eq = fieldExpression;
// 可为空类型转化为具体类型
if (prop.PropertyType.IsGenericType &&
prop.PropertyType.GetGenericTypeDefinition() == typeof(Nullable <>))
{
eq = Expression.Convert(fieldExpression, prop.PropertyType.GenericTypeArguments[0]);
}
else if (prop.PropertyType.IsEnum && filter.FieldValue is string)
{
eq = Expression.Call(fieldExpression, prop.PropertyType.GetMethod("ToString", Array.Empty <Type>()) !);
}
eq = filter.GetExpression(eq);
ret = Expression.Lambda <Func <TItem, bool> >(eq, p);
}
return(ret);
}
Expression <Func <TItem, bool> > GetComplexFilterExpression()
{
var p = Expression.Parameter(type);
var propertyNames = filter.FieldKey.Split('.');
PropertyInfo?pInfo = null;
Expression? fieldExpression = null;
foreach (var name in propertyNames)
{
if (pInfo == null)
{
pInfo = typeof(TItem).GetPropertyByName(name) ?? throw new InvalidOperationException($"the model {type.Name} not found the property {name}");
fieldExpression = Expression.Property(p, pInfo);
}
else
{
pInfo = pInfo.PropertyType.GetPropertyByName(name) ?? throw new InvalidOperationException($"the model {pInfo.PropertyType.Name} not found the property {name}");
fieldExpression = Expression.Property(fieldExpression, pInfo);
}
}
// 可为空类型转化为具体类型
if (pInfo !.PropertyType.IsGenericType && pInfo.PropertyType.GetGenericTypeDefinition() == typeof(Nullable <>))
{
fieldExpression = Expression.Convert(fieldExpression !, pInfo.PropertyType.GenericTypeArguments[0]);
}
