CODEWITHSUNDEEP
c#
Gucci
Gucci

Reputation: 931

Return different types of Lists<> in Method (C#)

At the moment I have a Method for executing database calls which returns a DataTable which is then converted into a List<>. Since I am using this Method for different database calls I need to make it return any List<>. This is at the moment not possible since I get an error:

Cannot convert List<T> to List<object>

What return type should the function have if i want to return any list? e.g. it could be that the result list is of the type:

List<MirrorDeployments>

or:

List<ProductionDeployments>

My Function

public List<T> Execute<T>(string strSql, List<T> list)
{
    using (OracleConnection conn = new OracleConnection(cnnStr))
    {
        using (OracleCommand objCommand = new OracleCommand(strSql, conn))
        {
            objCommand.CommandType = CommandType.Text;
            DataTable dt = new DataTable();
            OracleDataAdapter adp = new OracleDataAdapter(objCommand);
            conn.Open();
            adp.Fill(dt);
            if (dt != null)
            {

                list = ConvertToList(dt, list).ToList();
            }
        }
    }
    return list;
}

Upvotes: 0

Views: 685

Answers (1)

Alessandro D&#39;Andria
Alessandro D&#39;Andria

Reputation: 8868

Assuming that ConvertToList returns an enumerable of object:

public List<T> Execute<T>(string strSql)
{
    using (OracleConnection conn = new OracleConnection(cnnStr))
    {
        using (OracleCommand objCommand = new OracleCommand(strSql, conn))
        {
            objCommand.CommandType = CommandType.Text;
            DataTable dt = new DataTable();
            OracleDataAdapter adp = new OracleDataAdapter(objCommand);
            conn.Open();
            adp.Fill(dt);
            if (dt != null)
            {

                return ConvertToList(dt).Cast<T>().ToList();
            }
        }
    }
    return new List<T>();
}

I have removed the parameter list because seems useless.

A better option is to convert ConvertToList in a generic method ConvertToList<T> which does what its name say.

Upvotes: 2

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