fixed

Sieve/Services/SieveProcessor.cs

@@ -477,6 +477,7 @@ namespace Sieve.Services
                 }
                 outerExpression = Expression.And(outerExpression, innerExpression);
             }
+            
             var data = outerExpression == null
                 ? result
                 : result.Where(Expression.Lambda<Func<TEntity, bool>>(outerExpression, parameterExpression));
@@ -524,15 +525,16 @@ namespace Sieve.Services
                 case FilterOperator.LessThanOrEqualTo:
                     return Expression.LessThanOrEqual(propertyValue, filterValue);
                 case FilterOperator.Contains:
-                    return Expression.Call(propertyValue,
+                    //fixed bug has null in data
+                    return Expression.AndAlso(Expression.NotEqual(propertyValue, Expression.Constant(null, typeof(object))), Expression.Call(propertyValue,
                         typeof(string).GetMethods()
                         .First(m => m.Name == "Contains" && m.GetParameters().Length == 1),
-                        filterValue);
+                        filterValue));
                 case FilterOperator.StartsWith:
-                    return Expression.Call(propertyValue,
+                    return Expression.AndAlso(Expression.NotEqual(propertyValue, Expression.Constant(null, typeof(object))), Expression.Call(propertyValue,
                         typeof(string).GetMethods()
                         .First(m => m.Name == "StartsWith" && m.GetParameters().Length == 1),
-                        filterValue);
+                        filterValue));
                 default:
                     return Expression.Equal(propertyValue, filterValue);
             }