private static IEnumerable <string> GetOrderByClause(DataTableRequestModel pageRequestModel)
{
foreach (var detail in pageRequestModel.Order)
{
yield return(string.Format("{0} {1}", pageRequestModel.Columns[detail.Column].Data, detail.Dir));
}
}
private static IEnumerable <string> GetSearchClause(DataTableRequestModel pageRequestModel)
{
foreach (var tableColumn in pageRequestModel.Columns)
{
if (tableColumn.Searchable)
{
yield return(string.Format("{0} LIKE @0", tableColumn.Data));
}
}
}
public static IQueryable <T> GetExpression <T>(this DataTableRequestModel pageRequestModel, IQueryable <T> query) where T : class
{
ParameterExpression item = Expression.Parameter(typeof(T), "item");
Expression previousExpression = null;
Expression finalExpression = null;
IQueryable <T> results = null;
if (!string.IsNullOrEmpty(pageRequestModel.Search.Value))
{
foreach (var column in pageRequestModel.Columns)
{
if (!column.Searchable)
{
continue;
}
if (string.IsNullOrEmpty(column.Name))
{
continue;
}
var property = Expression.Property(item,
column.Data);
Expression leftExpression = Expression.Property(item,
column.Data);
//should not be null because we're going to do a contains..
bool typeIsString = false;
Expression likeneqResult = leftExpression;
if (property.Type == typeof(string))
{
Expression likeneqleft = leftExpression;
Expression likeneqright = Expression.Constant(null);
likeneqResult = Expression.NotEqual(likeneqleft,
likeneqright);
typeIsString = true;
}
//convert to string
var toString = typeof(Object).GetMethod("ToString");
var toStringValue = Expression.Call(leftExpression, toString);
//then we do a contains with IndexOf
var indexOf = Expression.Call(toStringValue, "IndexOf", null,
Expression.Constant(pageRequestModel.Search.Value, typeof(string)),
Expression.Constant(StringComparison.InvariantCultureIgnoreCase));
var like = Expression.GreaterThanOrEqual(indexOf, Expression.Constant(0));
//we check that the field is not null AND it contains
if (!typeIsString)
{
Expression likeneqright = Expression.Constant(null);
likeneqResult = Expression.NotEqual(toStringValue,
likeneqright);
}
Expression likeFinalExpress = Expression.AndAlso(likeneqResult,
like);
if (previousExpression == null)
{
finalExpression = likeFinalExpress;
}
else
{
finalExpression = Expression.Or(finalExpression,
likeFinalExpress);
}
previousExpression = likeFinalExpress;
}
if (finalExpression != null)
{
MethodCallExpression whereCallExpression = Expression.Call(typeof(Queryable),
"Where",
new Type[]
{
query.ElementType
},
query.Expression,
Expression.Lambda <Func <T, bool> >(finalExpression,
new ParameterExpression[]
{
item
}));
results = query.Provider.CreateQuery <T>(whereCallExpression);
}
else
{
results = query;
}
}
else
{
results = query;
}
if (pageRequestModel.Order.Any())
{
var order = pageRequestModel.Order[0];
var column = pageRequestModel.Columns[order.Column];
if (column.Orderable)
{
if (!string.IsNullOrEmpty(column.Name))
{
var type = typeof(T);
var property = type.GetProperty(column.Data);
var parameter = Expression.Parameter(type, "p");
var propertyAccess = Expression.MakeMemberAccess(parameter, property);
var orderByExp = Expression.Lambda(propertyAccess, parameter);
var typeArguments = new Type[] { type, property.PropertyType };
var methodName = ("asc".Equals(order.Dir, StringComparison.CurrentCultureIgnoreCase)) ? "OrderBy" : "OrderByDescending";
var resultExp = Expression.Call(typeof(Queryable), methodName, typeArguments, results.Expression, Expression.Quote(orderByExp));
results = results.Provider.CreateQuery <T>(resultExp);
}
}
}
//var startPage = (pageRequestModel.Length == 0) ? 1 : pageRequestModel.Start / pageRequestModel.Length + 1;
//return results.Skip((startPage - 1) * pageRequestModel.Length).Take(pageRequestModel.Length);
return(results);
}
