Keyword search to include Uniqueidentifier field - sql

Question

I'm wanting to let a user search rows in a database by specifying a keyword to look for. There are a few fields I would like to look in for this keyword, one of which is a uniqueidentifier. The problem is, if the keyword is not a GUID, I get the following error message:
Conversion failed when converting from a character string to uniqueidentifier
The SQL I'm using to run the search looks something like this:
// do not use
string sql = #"SELECT *
FROM [MyTable]
WHERE [MyTable].[TableID] = '" + keyword + "'";
WARNING: this is just example code - DO NOT write sql commands like this as it creates a security risk
How do I write my SQL select statement such that it will not fail when keyword is not a GUID?

Answer 1

string sql;
Guid id;
if (Guid.TryParse(keyword, out id))
{
sql = #"SELECT *
FROM [MyTable]
WHERE [MyTable].[TableID] = '" + keyword + "'";
}
else
{
sql = //search by other way
}

Answer 2

Does this work for you?
string sql = #"SELECT *
FROM [MyTable]
WHERE convert(varchar,[MyTable].[TableID]) = '" + keyword + "'";

Answer 3

I know this doesn't really help you today, but may help future readers. In SQL Server 2012 you will be able to use TRY_CONVERT:
string sql = #"SELECT *
FROM dbo.[MyTable]
WHERE [TableID] = TRY_CONVERT(UNIQUEIDENTIFIER, '" + keyword + "');";
But what you really should be doing is passing the parameter as a strongly typed GUID, and handling the error (using try/catch) in the client program when someone enters something that isn't a GUID.