Question

I have two methods that basically converts underlying checkboxes’ text or tag as CSV strings.

These two methods

• GetSelectedTextAsCsv()
• GetTagAsCsv()

differ only by which property to extract value from SelectedCheckBoxes, which is of type IList<CheckBox>

    public string GetSelectedTextAsCsv()     {         var buffer = new StringBuilder();         foreach (var cb in SelectedCheckBoxes)         {             buffer.Append(cb.Text).Append(',');         }         return DropLastComma(buffer.ToString());     }      public string GetTagAsCsv()     {         var buffer = new StringBuilder();         foreach (var cb in SelectedCheckBoxes)         {             buffer.Append(cb.Tag).Append(',');         }         return DropLastComma(buffer.ToString());     } 

I was trying to extract a method that returns a Func<T, TResult> but not sure how I can pull that off. My poor attempt was like the following but I cannot figure out how to extract the property portion as shown in the comment within ConvertToCsv()

    public Func<T, string> ConvertToCsv<T>()     {         return propertyName =>         {             var buffer = new StringBuilder();             foreach (var checkBox in SelectedCheckBoxes)             {                 buffer.Append(                     /* How can you abstract this portion? like following? */                      checkBox.propertyName                 ).Append(',');             }             return DropLastComma(buffer.ToString());         };     } 

If I am on a wrong track, would you please advise me on how I can refactor above code to use a common method?

[UPDATE 1] Here is the combination of both Brian and Jon’s answers

    public string ConvertToCsv<T>(Func<CheckBox, T> getValue)     {         var stringValues = SelectedCheckBoxes.Select(             cb => getValue(cb).ToString()).ToArray();         return string.Join(',', stringValues);     }      public string GetSelectedTextAsCsv()     {         return ConvertToCsv(cb => cb.Text);     }      public string GetTagAsCsv()     {         return ConvertToCsv(cb => cb.Tag);     } 

[UPDATE 2] version 2

    public string GetAsCsv<T>(Func<CheckBox, T> getValue)     {         return string.Join(',', SelectedCheckBoxes.Select(             cb => getValue(cb).ToString()).ToArray());     }      public string GetSelectedTextAsCsv()     {         return GetAsCsv(cb => cb.Text);     }      public string GetTagAsCsv()     {         return GetAsCsv(cb =>              cb.Tag == null ? string.Empty : cb.Tag.ToString());     } 

[UPDATE 3] Made the parameter of GetAsCsv() as a closed generic of CheckBox and string

Func<CheckBox, T> to Func<CheckBox, string>.

That allowed me to make GetAsCsv() even simpler and more readable.

private string GetAsCsv(Func<CheckBox, string> getValue) {     return string.Join(',', SelectedCheckBoxes.Select(getValue).ToArray()); } 

Answer 1

public string GetAsCsv(Func<CheckBox, string> getValue) {     var buffer = new StringBuilder();     foreach (var cb in SelectedCheckBoxes)     {         buffer.Append(getValue(cb)).Append(',');     }     return DropLastComma(buffer.ToString()); } 

Then:

GetAsCsv(cb => cb.Tag != null ? cb.Tag.ToString() : string.Empty); GetAsCsv(cb => cb.Text);