?????????????
string sql = @" if exists
(  select * FROM  [{0}].sys.extended_properties PFD with(nolock)
left join  [{0}].sys.columns C  with(nolock)
ON PFD.class=1 AND C.[object_id]=PFD.major_id AND C.column_id=PFD.minor_id
left JOIN  [{0}].sys.objects O with(nolock)
ON C.[object_id]=O.[object_id] AND O.type='U' AND O.is_ms_shipped=0
where C.name='{2}' and O.name='{1}' )
begin
USE [{0}];
EXEC sp_updateextendedproperty N'MS_Description'??   '{3}'??   N'user'??   N'dbo'??   N'table'??   N'{1}'??   N'column'??   N'{2}'
end
else
begin
USE [{0}];
EXECUTE   sp_addextendedproperty   N'MS_Description'??   '{3}'??   N'user'??   N'dbo'??   N'table'??   N'{1}'??   N'column'??   N'{2}'
end ";  //?ж???????????????????????????
dbName = dbName.Replace('''?? ' ');
sql = string.Format(sql?? dbName?? TableName?? rowName?? Description);
????????????????????????д?????????2??