Converting multiple method overloads to a general method, a design issue

Question

I am trying to reorganize some code here that was made earlier by other guys, as I find it quite impractical Here is an example

protected void SetParameterValue(SqlParameter parameter, string parameterValue, bool isNullable)
{
     if ((null == parameterValue || parameterValue == NULL_STRING) && isNullable)
            parameter.Value = DBNull.Value;
     else   parameter.Value = parameterValue;
}

protected void SetParameterValue(SqlParameter parameter, int parameterValue, bool isNullable)
{
     if (parameterValue == NULL_INT && isNullable)
            parameter.Value = DBNull.Value;
     else   parameter.Value = parameterValue;
}

protected void SetParameterValue( SqlParameter parameter, Int64 parameterValue, bool isNullable)
{
     if (parameterValue == NULL_LONG && isNullable)
            parameter.Value = DBNull.Value;
     else   parameter.Value = parameterValue;
}

Like these, there are many more. Now I needed to create one that accepts a new type (which does not yet have a method for it), and decided that maybe I can clean it up a bit, make it better. my idea is to create something like

protected void SetParameterValue<T>(SqlParameter parameter, T parameterValue, bool isNullable)

however, I do not know what the best approach is, what I can encapsulate inside this general method and what I need to do in separate methods. Is it worth it? or is the "many methods" approach okay? What will I get from the total? thank!

Answer 1

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private Dictionary<Type, Func<object, bool, bool>> _nullChecks = new Dictionary<Type, Func<object, bool, bool>>();

private void SetupNullChecks(){
    _nullChecks.Add(typeof(string), (object parameterValue, bool isNullable) => { return (null == parameterValue || parameterValue.ToString() == NULL_STRING) && isNullable; });
    _nullChecks.Add(typeof(int), (object parameterValue, bool isNullable) => { return (int)parameterValue == NULL_INT && isNullable; });
    _nullChecks.Add(typeof(long), (object parameterValue, bool isNullable) => { return (long)parameterValue == NULL_LONG && isNullable; });
}

:

public void SetParameterValue(SqlParameter parameter, object parameterValue, bool isNullable)
{
    if (_nullChecks[parameterValue.GetType()].Invoke(parameterValue, isNullable))
        parameter.Value = DBNull.Value;
    else parameter.Value = parameterValue;
}

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Answer 2

Protected void SetParameterValue(SqlParameter parameter, 
 object parameterValue, bool isNullable)....

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bool IsNull (object value){
   if (value is int){
     check int..
   }
}
//this is a quick and dirty example, there are more elegant ways to handle it.

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Answer 3

, bool isNullable.

protected void SetParameterValue<T>(SqlParameter parameter, T parameterValue)
{
if (parameterValue == null)
  parameter.Value = DBNull.Value;
else
  parameter.Value = parameterValue;
}

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Answer 4

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protected void SetParameterValue(SqlParameter parameter, int parameterValue, bool isNullable)
{
  SetParameterValue(parameter, (Int64)parameterValue, isNullable);
}
protected void SetParameterValue(SqlParameter parameter, Int64 parameterValue, bool isNullable)
{
  if (parameterValue == NULL_INT && isNullable)
    parameter.Value = DBNull.Value;
  else
    parameter.Value = parameterValue;
}

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Answer 5

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protected void SetParameterValue(SqlParameter parameter,object parameterValue){
    if(IsParameterNull(parameterValue) && parameter.IsNullable){
        parameter.Value = DBNull.Value;
    }
    else{
        parameter.Value = parameterValue;
    }
}

List<NULLTYPE> nulls = new List<NULLTYPE>(){new NULLTYPE(NULL_INT), new NULLTYPE(NULL_LONG), new NULLTYPE(null)}
protected bool IsParameterNull(object parameterValue){
    if(nulls.Contains(parameterValue)) return true;
    else return false;
}

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