/// <summary>
/// A shortcut methods to add a filter.
/// </summary>
/// <param name="filterColumnName"></param>
/// <param name="filterOperator"></param>
/// <param name="filterValue"></param>
/// <returns></returns>
public QueryModifiers AddFilter(string filterColumnName, DynamicFilterOperator filterOperator, object filterValue)
{
if (this.Filters == null)
{
this.Filters = new List <FilterInfo>();
}
this.Filters.Add(new FilterInfo {
FilterColumnName = filterColumnName, FilterOperator = filterOperator, FilterValue = filterValue
});
return(this);
}
public static ISelect <T1> Where <T1>(this ISelect <T1> select, string field, DynamicFilterOperator filterOperator, object value)
{
var filter = new DynamicFilterInfo {
Field = field, Operator = filterOperator, Value = value
};
Expression <Func <T1, bool> > exp = GetWhereExpression(select, filter);
return(select.Where(exp));
}
// ReSharper disable PossiblyMistakenUseOfParamsMethod
/// <summary>
/// Creates predicate expression that can be used in IQueryable[TEntity].Where(entity => entity.PropertyName FilterOperation FilterValue).
/// Got most from
/// http://stackoverflow.com/questions/8315819/expression-lambda-and-query-generation-at-runtime-simplest-where-example
/// </summary>
/// <typeparam name="TEntity"></typeparam>
/// <param name="propertyName">Entity property name</param>
/// <param name="dynamicFilterOperator">Filter operator, like Equal, StartsWith, Contains, LessThan, etc.</param>
/// <param name="filterValue">Filter value</param>
/// <returns></returns>
public static Expression <Func <TEntity, bool> > GetFilterPredicate <TEntity>(string propertyName, DynamicFilterOperator dynamicFilterOperator, object filterValue)
{
var entityExp = Expression.Parameter(typeof(TEntity), "entity");
var propertyExpression = Expression.Property(entityExp, propertyName);
Expression rvalue = Expression.Constant(filterValue);
Expression rvalueString = Expression.Constant(filterValue as string);
Expression boolExpression = null;
switch (dynamicFilterOperator)
{
case DynamicFilterOperator.Equal:
boolExpression = Expression.Equal(propertyExpression, rvalue);
break;
case DynamicFilterOperator.NotEqual:
boolExpression = Expression.NotEqual(propertyExpression, rvalue);
break;
case DynamicFilterOperator.GreaterThan:
boolExpression = Expression.GreaterThan(propertyExpression, rvalue);
break;
case DynamicFilterOperator.GreaterThanOrEqual:
boolExpression = Expression.GreaterThanOrEqual(propertyExpression, rvalue);
break;
case DynamicFilterOperator.LessThan:
boolExpression = Expression.LessThan(propertyExpression, rvalue);
break;
case DynamicFilterOperator.LessThanOrEqual:
boolExpression = Expression.LessThanOrEqual(propertyExpression, rvalue);
break;
case DynamicFilterOperator.StringStartsWith:
boolExpression = Expression.Call(propertyExpression, stringStartsWithMethod, rvalueString);
break;
case DynamicFilterOperator.StringContains:
boolExpression = Expression.Call(propertyExpression, stringContainsMethod, rvalueString);
break;
}
if (boolExpression == null)
{
throw new InvalidOperationException();
}
Expression <Func <TEntity, bool> > exp = Expression.Lambda <Func <TEntity, bool> >(boolExpression, entityExp);
return(exp);
}
