Change Data Type Varchar to Varbinary(Max) in SQL Server

Change column from VARCHAR(MAX) to VARBINARY(MAX)

You cannot perform this conversion using an ALTER TABLE statement since converting from varchar(max) to varbinary(max) requires an explicit conversion. So you should follow these steps to alter your table:

1. Alter table with new column of VARBINARY(MAX)
2. If you have existing data in the VARCHAR(MAX) column, use update statement to add the data to the VARBINARY column
3. Alter table to drop the VARCHAR(MAX) column
4. Rename varbinary column to varchar name (per comment from @Ben Thul)

Implicit conversion from data type varchar to varbinary is not allowed. (SQL)

Either the field Nombre or Descripcion is a varbinary and you must explicitly convert those inputs for your insert clause.

It would look like this.

VALUES (... ,CONVERT(varbinary, [@Nombre or @Descripcion]) ,...)

Error converting VarChar to VarBinary in SQL Server

Hmm, AFEE27AF97DC6 is one nibble short and it seems like only full bytes are accepted. Try to zero pad it. E.g.

SELECT convert(varbinary(max), '0AFEE27AF97DC6', 2)

You can also wrap it in a CASE expression checking if the string has an even or odd length, should the strings be variable.

SELECT convert(varbinary(max),
               CASE
                 WHEN len('AFEE27AF97DC6') % 2 <> 0 THEN
                   concat('0', 'AFEE27AF97DC6')
                 ELSE
                   'AFEE27AF97DC6'
               END,
               2)

(Replace the literals with your variable.)

Convert varchar(max) to varbinary(max)

you are using wrong Syntax for CONVERT

https://msdn.microsoft.com/en-in/library/ms187928.aspx

-- Syntax for CONVERT:  
CONVERT ( data_type [ ( length ) ] , expression [ , style ] )  

try to use this

update DocumentOnline
set FileData = CONVERT(VARBINARY(max),  0x255044462D312E340A25E2E3CFD30A322030206F626A0A3C3C2F4C656E6774682034392F46696C7465722F466C6174654465636F64653E3E73747265616D0A789C2BE4720AE1323653B03030530849E1720DE10AE42A54305430004208999CABA01F9166A8E092AF10C80500EAA209F20A656E6473747265616D0A656E646F626A0A342030206F626A0A3C3C2F5265736F75726365733C3C2F584F626A6563743C3C2F586631203120) 
where ClientId = '54528' and EndDate = '201607'

Implicit conversion from data type varchar to varbinary(max) is not allowed c#

I think that better solution will be using SqlParameter like this:

cmd.Parameters.Add("@Biometric", SqlDbType.VarBinary, 8000).Value = bTemplateDataOne;

Error converting data type varchar to varbinary in sql only for few values

You're passing a style of 1 to CONVERT.

If the data_type is a binary type, the expression must be a character expression. The expression must be composed of an even number of hexadecimal digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, a, b, c, d, e, f). If the style is set to 1 the characters 0x must be the first two characters in the expression. If the expression contains an odd number of characters or if any of the characters are invalid an error is raised.

My emphasis.

All of your examples of invalid sequences appear to have odd lengths. You should add a padding 0 if you have an odd length sequence. Whether you pad at the start or the end depends on your exact requirements, where the sequence came from, etc.

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