A simple named format implementation

NamedFormat.cs

public static string NamedFormat(string format, params object[] args)
{
    var newFormat = string.Empty;
    var paraIndex = 0;
    var paraNameIndexMap = new Dictionary<string, int>();
    for (int i = 0; i < format.Length; i++)
    {
        var ch = format[i];
        if (ch == '{')
        {
            var paraName = string.Empty;
            for (i++; i < format.Length; i++)
            {
                ch = format[i];
                if (ch == '}')
                {
                    break;
                }
                paraName += ch;
            }
            if (ch == '}')
            {
                if (paraNameIndexMap.ContainsKey(paraName))
                {
                    newFormat += "{" + paraNameIndexMap[paraName] + "}";
                }
                else
                {
                    newFormat += "{" + paraIndex + "}";
                    paraNameIndexMap[paraName] = paraIndex;
                    paraIndex++;
                }
            }
        }
        else
        {
            newFormat += ch;
        }
    }

    if (paraIndex > args.Length)
    {
        throw new FormatException($"The format {format} specified more parameters than the parameters passed in");
    }

    return string.Format(newFormat, args);
}