FIX: Encoding Decoding Github issue

mssql_python/connection.py

@@ -386,6 +386,12 @@ def setencoding(self, encoding=None, ctype=None):
                 ddbc_error=f"ctype must be SQL_CHAR ({ConstantsDDBC.SQL_CHAR.value}) or SQL_WCHAR ({ConstantsDDBC.SQL_WCHAR.value})",
             )
 
+        # Enforce UTF-16 encoding restriction for SQL_WCHAR
+        if ctype == ConstantsDDBC.SQL_WCHAR.value and encoding not in UTF16_ENCODINGS:
+            log('warning', "SQL_WCHAR only supports UTF-16 encodings. Attempted encoding '%s' is not allowed. Using default 'utf-16le' instead.", 
+                sanitize_user_input(encoding))
+            encoding = 'utf-16le'
+
         # Store the encoding settings
         self._encoding_settings = {
             'encoding': encoding,
@@ -489,13 +495,26 @@ def setdecoding(self, sqltype, encoding=None, ctype=None):
         # Normalize encoding to lowercase for consistency
         encoding = encoding.lower()
 
+        # Enforce UTF-16 encoding restriction for SQL_WCHAR and SQL_WMETADATA
+        if (sqltype == ConstantsDDBC.SQL_WCHAR.value or sqltype == SQL_WMETADATA) and encoding not in UTF16_ENCODINGS:
+            sqltype_name = "SQL_WCHAR" if sqltype == ConstantsDDBC.SQL_WCHAR.value else "SQL_WMETADATA"
+            log('warning', "%s only supports UTF-16 encodings. Attempted encoding '%s' is not allowed. Using default 'utf-16le' instead.", 
+                sqltype_name, sanitize_user_input(encoding))
+            encoding = 'utf-16le'
+
         # Set default ctype based on encoding if not provided
         if ctype is None:
             if encoding in UTF16_ENCODINGS:
                 ctype = ConstantsDDBC.SQL_WCHAR.value
             else:
                 ctype = ConstantsDDBC.SQL_CHAR.value
 
+        # Additional validation: if user explicitly sets ctype to SQL_WCHAR but encoding is not UTF-16
+        if ctype == ConstantsDDBC.SQL_WCHAR.value and encoding not in UTF16_ENCODINGS:
+            log('warning', "SQL_WCHAR ctype only supports UTF-16 encodings. Attempted encoding '%s' is not compatible. Using default 'utf-16le' instead.", 
+                sanitize_user_input(encoding))
+            encoding = 'utf-16le'
+
         # Validate ctype
         valid_ctypes = [ConstantsDDBC.SQL_CHAR.value, ConstantsDDBC.SQL_WCHAR.value]
         if ctype not in valid_ctypes: