Pad left or right with string.format (not padleft or padright) with arbitrary string
Solution 1:
There is another solution.
Implement IFormatProvider
to return a ICustomFormatter
that will be passed to string.Format :
public class StringPadder : ICustomFormatter
{
public string Format(string format, object arg,
IFormatProvider formatProvider)
{
// do padding for string arguments
// use default for others
}
}
public class StringPadderFormatProvider : IFormatProvider
{
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter))
return new StringPadder();
return null;
}
public static readonly IFormatProvider Default =
new StringPadderFormatProvider();
}
Then you can use it like this :
string.Format(StringPadderFormatProvider.Default, "->{0:x20}<-", "Hello");
Solution 2:
You could encapsulate the string in a struct that implements IFormattable
public struct PaddedString : IFormattable
{
private string value;
public PaddedString(string value) { this.value = value; }
public string ToString(string format, IFormatProvider formatProvider)
{
//... use the format to pad value
}
public static explicit operator PaddedString(string value)
{
return new PaddedString(value);
}
}
Then use this like that :
string.Format("->{0:x20}<-", (PaddedString)"Hello");
result:
"->xxxxxxxxxxxxxxxHello<-"
Solution 3:
Edit: I misunderstood your question, I thought you were asking how to pad with spaces.
What you are asking is not possible using the string.Format
alignment component; string.Format
always pads with whitespace. See the Alignment Component section of MSDN: Composite Formatting.
According to Reflector, this is the code that runs inside StringBuilder.AppendFormat(IFormatProvider, string, object[])
which is called by string.Format
:
int repeatCount = num6 - str2.Length;
if (!flag && (repeatCount > 0))
{
this.Append(' ', repeatCount);
}
this.Append(str2);
if (flag && (repeatCount > 0))
{
this.Append(' ', repeatCount);
}
As you can see, blanks are hard coded to be filled with whitespace.