Stored procedure runs fine from SSMS but fails when called from the C# app

Question

I'm using SS Express 2012 so I doubt I have all possible debugging capabilities at my disposal, although I'm still trying to figure this out myself.
The compiled C# application has logging to insure that the the SP is being invoked, the appropriate line of code is  definitely being reached. The logging always reports 'success' suggesting that the SP was successfully executed (and no exception is thrown
to the C# app), but the indexes aren't getting rebuilt (I have a fragmentation query proving they are not rebuilt). Yet it runs successfully if I
    (1) set a breakpoint in the C# app and step through the code line by line OR
    (2) run the SP from the SSMS GUI.
The fragmentation query confirms sucess for both 1 and 2.
-I can't rely on the GUI because I want to run this overnight immediately after the C# app is finished inserting new records.
- The SP loops through all the tables, and all the indexes in each table, checking for fragmentation and rebuilding any indexes over 7% fragmented.
ALTER Procedure [dbo].[usp_RebuildIndexes]
AS
Declare @fetch_TableName NVARCHAR(256)
DECLARE Cursor_Tables CURSOR FOR
SELECT Name FROM sysobjects WHERE xtype ='U'
OPEN Cursor_Tables
While 1 = 1 -- Begin to Loop through all tables
BEGIN
FETCH NEXT FROM Cursor_Tables INTO @fetch_TableName -- fetches the next table
if @@FETCH_STATUS <> 0 break
print '---------' + @fetch_TableName
Declare @fetch_indexName NVARCHAR(256) -- loops through al indexes of the current table
DECLARE Cursor_Indexes CURSOR FOR -- Looking for indexes fragmented more than 7 percent.
SELECT name as indexName
FROM sys.dm_db_index_physical_stats (DB_ID(DB_Name()), OBJECT_ID(@fetch_TableName), NULL, NULL, NULL) AS a
JOIN sys.indexes AS b ON a.object_id = b.object_id AND a.index_id = b.index_id
Where Name is not null and avg_fragmentation_in_percent > 7
OPEN Cursor_Indexes
WHILE 1= 1 -- Begin to Loop through all Indexes
BEGIN
FETCH NEXT FROM [Cursor_Indexes] INTO @fetch_indexName
if @@FETCH_STATUS <> 0 break
Declare @SqL nvarchar(2000) = N'ALTER INDEX ' + @fetch_indexName + ' ON ' + DB_Name() + '.dbo.' + @fetch_TableName + ' Rebuild'
print @Sql
Begin TRy
Execute sp_executeSQL @sql
End Try
Begin Catch
Declare @err nvarchar(2000) = ERROR_MESSAGE();
throw 51000, @err, 1
End Catch
End -- Ends looping through all indexes
CLOSE [Cursor_Indexes]
DEALLOCATE [Cursor_Indexes]
End -- Ends looping through all tables
CLOSE Cursor_Tables
DEALLOCATE Cursor_Tables
foreach (objDB DB in oUserPrefs.DBs) {
report += DB.Real_Name;
if (DB.cn == null) DB.cn = sqlCn(DB.Real_Name, SystemInformation.ComputerName);
try {
if (DB.cn.State != ConnectionState.Open) DB.cn.Open();
} catch (Exception ex) {
report += " - Failed because can't open a connection.\r\n";
continue;
DB.OpenedAConnection = true;
DataTable dt = null;
try {
dt = oParam.fillDt("dbo.usp_RebuildIndexes", DB.cn, null);
} catch (Exception ex) {
report += " -failed because " + ex.Message + "\r\n\r\n";
continue;
report += " - success.\r\n";
DB.LastTimeRebuiltIndexes = DateTime.Now;

Answer 1

Your proc is a bit of a mess and hard to read. This should get you what you need though. I added a little logic in the middle that determines if the index should be reorged, or rebuilt.
You were right that my script was too messy and I used your code/logic to rewrite mine. Thanks! I tried it this morning and it worked fine, but I will have to see how it runs overnight to be sure.
Here's the weird thing. My original code should have worked. In fact I'm actually using it in 3 c-sharp apps each of which has 3 to 7  Express 2012 databases (about 10 million records per database). For about a month it's been working fine on two of the
apps. Furthermore this morning I used a commercial file-comparison tool to verify that the 3rd app has been running an identical version of the SP. So I'm at a total loss as to what went wrong in the 3rd app.
Here's my rewrite.
Alter Procedure [dbo].[usp_RebuildIndexes]
As
Declare @Messages Table(Msg nvarchar(2000))
Declare @IndexName nvarchar(256), @TableName NVARCHAR(256)
DECLARE Cursor_Indexes CURSOR FAST_FORWARD FOR -- GEt a list of all indexes for all tables.
select idxs.name as indexName, o.Name as TableName
from sys.indexes idxs
inner join sysobjects o on idxs.object_id = o.id
inner join sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL,NULL,NULL) as stats
on stats.object_id = idxs.object_id and stats.index_id = idxs.index_id
where xtype = 'u' and idxs.name is not null And avg_fragmentation_in_percent > 7
OPEN Cursor_Indexes
While 1 = 1
BEGIN
FETCH NEXT FROM Cursor_Indexes INTO @IndexName, @TableName
if @@FETCH_STATUS <> 0 break
Declare @SqL nvarchar(2000) = N'ALTER INDEX ' + @IndexName + ' ON ' + DB_Name() + '.dbo.' + @TableName + ' Rebuild'
insert @Messages(Msg)VALUES(@sql)
Execute sp_executeSQL @sql
End
CLOSE [Cursor_Indexes]
DEALLOCATE [Cursor_Indexes]
Select * From @Messages