1.Start VisualSVN Server Manager
2.Under Repositories, Select your repository and then Open Properties
3.Select Hooks tab
4.double click the pre-commit hook
Edit: As of VisualSVN version 2.5 use below code
setlocal enabledelayedexpansion
set REPOS=%1
set TXN=%2
set SVNLOOK="%VISUALSVN_SERVER%\bin\svnlook.exe"
SET M=
REM Concatenate all the lines in the commit message
FOR /F "usebackq delims==" %%g IN (`%SVNLOOK% log -t %TXN% %REPOS%`) DO SET M=!M!%%g
REM Make sure M is defined
SET M=0%M%
REM Here the 6 is the length we require
IF NOT "%M:~6,1%"=="" goto NORMAL_EXIT
:ERROR_TOO_SHORT
echo "Commit note must be at least 6 letters" >&2
goto ERROR_EXIT
:ERROR_EXIT
exit /b 1
REM All checks passed, so allow the commit.
:NORMAL_EXIT
exit 0
If using VisualSVN \< 2.5
setlocal
set REPOS=%1
set TXN=%2
set SVNLOOK="C:\Program Files\VisualSVN Server\bin\svnlook.exe"
REM Make sure that the log message contains some text.
FOR /F "usebackq delims==" %%g IN (`%SVNLOOK% log -t %TXN% %REPOS% FINDSTR /R /C:......`) DO goto NORMAL_EXIT
:ERROR_TOO_SHORT
echo "Comment must be at least 6 letters" >&2
goto ERROR_EXIT
:ERROR_EXIT
exit /b 1
REM All checks passed, so allow the commit.
:NORMAL_EXIT
exit 0
The above code will make the comment of at least 6 letters mandatory.