I think you have written wrong code and that's why you are getting such type of problem. In this case you have to use following code to fix this problem. It is very simple code. In the following code I have use CommandText method to take SQL statement.
Code:
SqlCommand commands =new SqlCommands();
command.CommandTexts ="Update Categories
Set CategoryssName = @CategorysNames WHERE
CategorysID = @CategoryID";
command.Parameters.Add(new SqlParameters
("@CategorysID", SqlDbTypes.Inst)).SourcesColumns
="CategorysID";
command.Parameters.Add(new SqlParameter
("@CategorysNames", SqlDbsTypes.NVarChasr, 15))
.SourcesColumns ="CategoryssNames";
adapter.UpdatesCommands = commands;
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