private MemberExpression GetPropertyAccess(ParameterExpression arg)
{
string[] parts = QueryKey.Split('.');
MemberExpression property = Expression.Property(arg, parts[0]);
for (int i = 1; i < parts.Length; i++)
{
property = Expression.Property(property, parts[i]);
}
return(property);
}
private Expression <Func <T, bool> > CreatePredicateWithNullCheck <T>(Expression searchExpression, ParameterExpression arg, MemberExpression targetProperty)
{
string[] parts = QueryKey.Split('.');
Expression nullCheckExpression = null;
if (parts.Length > 1)
{
MemberExpression property = Expression.Property(arg, parts[0]);
nullCheckExpression = Expression.NotEqual(property, Expression.Constant(null));
for (int i = 1; i < parts.Length - 1; i++)
{
property = Expression.Property(property, parts[i]);
Expression innerNullCheckExpression = Expression.NotEqual(property, Expression.Constant(null));
nullCheckExpression = Expression.AndAlso(nullCheckExpression, innerNullCheckExpression);
}
}
if (!targetProperty.Type.IsValueType || (targetProperty.Type.IsGenericType && targetProperty.Type.GetGenericTypeDefinition() == typeof(Nullable <>)))
{
var innerNullCheckExpression = Expression.NotEqual(targetProperty, Expression.Constant(null));
if (nullCheckExpression == null)
{
nullCheckExpression = innerNullCheckExpression;
}
else
{
nullCheckExpression = Expression.AndAlso(nullCheckExpression, innerNullCheckExpression);
}
}
if (nullCheckExpression == null || ValueFromQuery == null)
{
return(Expression.Lambda <Func <T, bool> >(searchExpression, arg));
}
else
{
var combinedExpression = Expression.AndAlso(nullCheckExpression, searchExpression);
var predicate = Expression.Lambda <Func <T, bool> >(combinedExpression, arg);
return(predicate);
}
}