C#

Int64 i = 100000000;
Console.WriteLine( i.ToString( "### ### ###" ).TrimStart() );

NumberFormatInfo nfi = (NumberFormatInfo)CultureInfo.InvariantCulture.NumberFormat.Clone();
nfi.NumberGroupSeparator = " ";
int yourNumber=123456789;
string yourFormattedNumber = yourNumber.ToString("#,0", nfi);

long number = 100000000000;
string value = string.Format("{0:#,##0}", number).Replace(",", " ");

public string HowManyMillion(int millions, string suffix) => $"{millions / 1000000} {suffix}";

// use example: string millions = HowManyMillion(100000000, "miliarde");

this.tabControl_Schedules.TabPages[tabpage_counter].Controls["button" + announcement_counter++].ImageIndex = 1;

Button butt = new Button();
butt = (Button)this.tabControl_Schedules.TabPages[tabpage_counter].Controls["button" + announcement_counter++];

butt.ImageIndex = 1;

Member 14271084 wrote:

C#

Button butt = new Button();
butt = ...

// Either:
Button butt;
butt = (Button)this.tabControl_Schedules.TabPages[tabpage_counter].Controls["button" + announcement_counter++];

// Or:
Button butt = (Button)this.tabControl_Schedules.TabPages[tabpage_counter].Controls["button" + announcement_counter++];

// untested code

public Dictionary<string, Button> BtnDict = new Dictionary<string, Button>();

public void AddNewButton(ImageList btnimagelist, Control btnsite, string btntext, int btnimgindex, Point btnlocation)
{
    Button btn = new Button
    {
        Text = btntext,
        ImageList = btnimagelist,
        ImageIndex = btnimgindex,
        Location = btnlocation
    };

    btnsite.Controls.Add(btn);
}

public void IncBtnImage(string btntext)
{
    Button btn = BtnDict[btntext];

    int icnt = btn.ImageList.Images.Count;

    int ndx = ++btn.ImageIndex;

    if (ndx == icnt) ndx = 0; // assumes you return to first image

    btn.ImageIndex = ndx;
}

https://google.github.io/styleguide/jsoncstyleguide.xml[^]

Property names must conform to the following guidelines:

Property names should be meaningful names with defined semantics.
Property names must be camel-cased, ascii strings.
The first character must be a letter, an underscore (_) or a dollar sign ($).
Subsequent characters can be a letter, a digit, an underscore, or a dollar sign.
Reserved JavaScript keywords should be avoided (A list of reserved JavaScript keywords can be found below).

public class IsoDateTimeFormatConverter : IsoDateTimeConverter
{
    public IsoDateTimeFormatConverter(string format)
    {
        DateTimeFormat = format;
    }
}

public class CustomFields
{
    [JsonProperty("post-date")]
    [JsonConverter(typeof(IsoDateTimeFormatConverter), "yyyy-MM-dd")]
    public DateTimeOffset PostDate { get; set; }
}

public class Root
{
    [JsonProperty("custom-fields")]
    public CustomFields CustomFields { get; } = new CustomFields();
}

...

var x = new Root
{
    CustomFields = 
    {
        PostDate = DateTime.Today
    }
};

string json = JsonConvert.SerializeObject(x);
// Output: {"custom-fields":{"post-date":"2019-04-16"}}

public class Root
{
    [JsonProperty("custom-fields")]
    public Dictionary<string, object> CustomFields { get; } = new Dictionary<string, object>();
}

...

var x = new Root
{
    CustomFields = 
    {
        ["post-date"] = DateTime.Today.ToString("yyyy-MM-dd")
    }
};

string json = JsonConvert.SerializeObject(x);
// Output: {"custom-fields":{"post-date":"2019-04-16"}}

Console.WriteLine(JsonConvert.SerializeObject(x));