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carallot
Asked: 2021-10-23 09:05:35 +0800 CST 2021-10-23 09:05:35 +0800 CST

Asynchronous database queries

  • 772

Good I have a big mess with asynchronous programming. When I query the API of an online store, I always use the await. When I implement these in a method, I always return the result with Task<T>. However, when I try to do the same thing with queries to a database, I get the error:

Error CS1061 "int" does not contain a definition for "GetAwaiter" or an accessible extension method "GetAwaiter" that accepts a first argument of type "int" (are you missing a using directive or an assembly reference?) An example of what i try to do:

public async Task<Int32> ObteNumFills()
{
    Int32 nRegs = 0;
    string connectionString = Cconnexio.RetornaCadenaConnexio(BddParams);
    string query= "Select COUNT(codigo) FROM empleados where edad > 24;
    using (SqlConnection cn = new SqlConnection(connectionString))
    {
        cn.Open();
        SqlCommand cmd = new SqlCommand(query, cn);
        try
        {
            nRegs = await(Int32)cmd.ExecuteScalar();
        }
        catch (Exception e)
        {

            nRegs = 0;
        }
    }
    return nRegs;
}

This query is very simple and shouldn't take more than a few milliseconds, but how could I perform this task asynchronously?

c#

1 Answers

  1. Best Answer

    You have to use the async methods cn.OpenAsync()andcmd.ExecuteScalarAsync()

    public async Task<Int32> ObteNumFills()
{
    Int32 nRegs = 0;
    string connectionString = Cconnexio.RetornaCadenaConnexio(BddParams);
    string query= "Select COUNT(codigo) FROM empleados where edad > 24";
    using (SqlConnection cn = new SqlConnection(connectionString))
    {
        //       |
        //       V
        await cn.OpenAsync();
        SqlCommand cmd = new SqlCommand(query, cn);
        try
        {
            //                         |
            //                         V   
            nRegs = (Int32)(await cmd.ExecuteScalarAsync());
        }
        catch (Exception e)
        {

            nRegs = 0;
        }
    }
    return nRegs;
}
    • 1