Using Dapper-dot-net, how do I map SQL uniqueidentifier column to a .Net type?

.net, dapper, t-sql

Solution

Aha! It appears that you must convert the SQL uniqueidentifier to a string in T-SQL and then map to to a string type in .Net.

string sql = @"SELECT TOP 100
               CONVERT(varchar(36), MyIdColumn) AS IdColumnString
               FROM MyTable";

conn.Query<string>(sql).ToList();

I assume special care would need to be taken converting back from .Net string to T-SQL uniqueidentifier on updates, but I have not yet tested that concern.

Problem

I have an existing database that uses the SQL "uniqueidentifier" type, which looks like a different GUID format than a .Net GUID. Question: Using Dapper, how do I map SQL uniqueidentifier column to .Net? Issue: Using Dapper-dot-net, when I map the column using the .Net GUID type, it compiles and runs, but all of the .ToString() output displays the same incorrect GUID. (well it doesn't match what I see in SSMS) When I try to map the column using the string type, I get a compiler error. Ideas? Is this possible?

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