Non-Stored Procedure Query (CommandType=Text) with Dapper and parameters

Question

Non-Stored Procedure Query (CommandType=Text) with Dapper and parameters

c# dapper

Question

I am trying to call a piece of SQL with parameters in Dapper. It is NOT a stored procedure (I have that working fine with parameters)

inputCustomerName = "Our Customer";
inputStationName  = Null;

    var parameters = new
    {
        customerName = inputCustomerName ,
        stationName = inputStationName    
    };     

    ...

    using (var dbConn = dataProvider.CreateConnection)
    {
        dbConn.ConnectionString = connectionString;
        dbConn.Open();
        returnValue = dbConn.Query<T>(sql: sql, commandType: commandType, param: parameters);
        dbConn.Close();
    }

The relevant part of the SQL is

"    ...

     WHERE 
        Customer = ISNULL(@customerName,Customer)
        AND Station = ISNULL(@stationName,Station)
";

I keep getting "Invalid type owner for DynamicMethod". (I got this also when using DynamicParameters instead of the anomymous object).

The SQL runs fine on the database itself (given I declare and @populate @customerName and stationName).

I suspect I have done something quite simple wrong - can anyone enlighten me?

kpollock

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kpollock · Accepted Answer · 5/4/2017 1:49:15 PM

The answer was, in the end, an issue in code not included in the question - for which I thoroughly apologise.

The issue was that T was an Interface, and that was what was causing Dapper to blow up. There's probably something under the hood that means you can only use classes, not interfaces as the type param to Query. Though I have never seen that restriction explicitly stated.

Shame, (but I can imagine a few reasons why)

Non-Stored Procedure Query (CommandType=Text) with Dapper and parameters

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