C# – Comparing QUERY and EXECUTE in Dapper

cdapper

I would like to ask if what is the best to use when INSERTING, UPDATING, DELETING, REMOVING, QUERY SPECIFIC DATA using DAPPER? I'm really confused in using EXECUTE and QUERY command in DAPPER..

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This should not be confusing at all, especially if you look at the signature of the methods exposed by the Dapper (as per documentation):

public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null, bool buffered = true)

Query method is specifically meant for executing a select statement internally, which can return the IEnumerable of a type T, there are options to execute it, if done using anonymous parameter, then you are not expecting any return value or Output parameter, it just takes input parameter and provide the result, which has schema matching to the properties of Type T. In case return value or Output parameter is required, then that needs to be bound using DynamicParameters

public static int Execute(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null)

Execute method is meant for executing the DML statements, like Insert, Update and Delete, whose purpose is to make changes to the data in the database. The return type is an integer, which should contain the value of number of rows updated, if in SQL Server we have set Set RowCount On, this call will not help in returning the Result Set, its only for DML calls.

In case you need multiple result set then we have QueryMultiple. which returns a GridReader and can be used to return the result of multiple Select statements, using a concept of MARS (Multiple active result set).

Practically if your aim is just to execute a procedure, any of them would do, but what is more important is what result set are looking forward to receive, they all have different return to provide results

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

Best Answer

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C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – the difference between const and readonly in C#

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