Using named parameter only when passing integer

问题

Currently I'm trying to work with Named Parameters using SAP Sybase SQL Anywhere 12 with dapper. The following codes runs correctly:

public class Test
{
    public int Str1
    {
        get;
        set;
    }

    public string Str2
    {
        get;
        set;
    }
}

class Program
{
    static void Main(string[] args)
    {
        using (SAConnection connection = new SAConnection("..."))
        {
            connection.Open();

            Test test = connection.Query<Test>("SELECT :Str1 as Str1, :Str2 as Str2",
                new Test() { Str1 = 35, Str2 = "42" }).FirstOrDefault();                    

            Console.WriteLine($"Str1: {test.Str1} | Str2: {test.Str2}");
            Console.ReadLine();
        }
    }
}

But when i change Str2 = "42" to some string, than i get the following exception:

Cast 42a to integer not possible

This exception is thrown when I'm using the following code:

Test test = connection.Query<Test>("SELECT :Str1 as Str1, :Str2 as Str2",
new Test() { Str1 = 35, Str2 = "42a" }).FirstOrDefault();

Is there some known issue? This should work correctly, cause i just want to pass a string around.

Edit

Stack trace:

iAnywhere.Data.SQLAnywhere.SAException (0x80004005): Umwandeln von '42a' auf integer nicht möglich bei iAnywhere.Data.SQLAnywhere.SACommand._ExecuteReader(CommandBehavior commandBehavior, Boolean isExecuteScalar, Boolean isBeginExecuteReader) bei iAnywhere.Data.SQLAnywhere.SACommand.ExecuteDbDataReader(CommandBehavior behavior) bei System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior) bei Dapper.SqlMapper.d__611.MoveNext() bei System.Collections.Generic.List1..ctor(IEnumerable1 collection) bei System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) bei Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable1 commandTimeout, Nullable1 commandType) bei DapperSqlAnywhere.Program.Main(String[] args) in C:\Users....\DapperSqlAnywhere\Program.cs:Zeile 35.

Thanks a lot!

回答1:

I don't know a great deal about SQLAnywhere but in your 1st select statement is being parsed as

SELECT 35 as Str1, 42 as Str2

which is fine because they're both integers Your 2nd statement

SELECT 35 as Str1, 42a as Str2

should probably be

SELECT 35 as Str1, '42a' as Str2

So I'd try changing the code to

Test test = connection.Query<Test>("SELECT :Str1 as Str1, ':Str2' as Str2",
            new Test() { Str1 = 35, Str2 = "42" }).FirstOrDefault();

来源：https://stackoverflow.com/questions/37751770/using-named-parameter-only-when-passing-integer

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