How to insert a C# List to database using Dapper.NET

You’d have to do it a little differently. In Dapper, it matches on convention AKA property or field names being identical to SQL parameters. So, assuming you had a MyObject:

public class MyObject
{
    public int A { get; set; }

    public string B { get; set; }
}

And assuming processList = List<MyObject>, You’d want to do this

foreach (var item in processList)
{
    string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
    connection.Execute(processQuery, item);
}

Note that the MyObject property names A and B match the SQL parameter names @A and @B.

If you don’t want to rename objects, you can use anonymous types to do the mappings instead of concrete types:

foreach (var item in processList)
{
    string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
    connection.Execute(processQuery, new { A = item.A, B = item.B });
}

EDIT:

Per Marc Gravell’s comment, you can also have Dapper do the loop for you:

string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
connection.Execute(processQuery, processList);