I am trying to filter a csv file from quotation marks. This line strangely deletes all the quotation marks in the line:
before : "NewClient"Name"
foo = foo.Replace(foo.Substring(0, 1), "");
after : NewClientName
Why is this happening? Shouldn't the Replace() method just delete the first occurence?
Usually when working with CSV we double quotations:
a -> "a"
a"b -> "a""b"
NewClient"Name -> "NewClient""Name"
To cut such a quotation, i.e.
"NewClient""Name" -> NewClient"Name
when "NewClient"Name" being a syntax error you can try
private static string CutQuotation(string value) {
if (string.IsNullOrEmpty(value))
return value;
else if (!value.Contains('"'))
return value;
if (value.Length == 1)
throw new FormatException("Incorrect quotation format: string can't be of length 1.");
else if (value[0] != '"')
throw new FormatException("Incorrect quotation format: string must start with \".");
else if (value[value.Length - 1] != '"')
throw new FormatException("Incorrect quotation format: string must end with \".");
StringBuilder builder = new StringBuilder(value.Length);
for (int i = 1; i < value.Length - 1; ++i)
if (value[i] == '"')
if (i == value.Length - 2)
throw new FormatException("Incorrect quotation format. Dangling \".");
else if (value[++i] == '"')
builder.Append(value[i]);
else
throw new FormatException("Incorrect quotation format. Dangling \".");
else
builder.Append(value[i]);
return builder.ToString();
}
As you can see, it's not just single Replace() routine.
Tests:
// abc - no quotation
Console.WriteLine(CutQuotation("abc"));
// abc - simple quotation cut
Console.WriteLine(CutQuotation("\"abc\""));
// "abc" - double quotation
Console.WriteLine(CutQuotation("\"\"abc\"\""));
// a"bc - quotation in the middle
Console.WriteLine(CutQuotation("\"a\"\"bc\""));
Shouldn't the replace method just delete the first occurence?
You would think so, because you're using Substring(0, 1):
string foo = "\"NewClient\"Name\"";
foo = foo.Replace(foo.Substring(0, 1), "");
But the substring is obtained before the call to Replace(). In other words, your Substring() and Replace() have no relation to each other whatsoever, so the code is equivalent to:
string foo = "\"NewClient\"Name\"";
foo = foo.Replace("\"", "");
And String.Replace() replaces all occurrences.
If you only want to replace the first instance, see How do I replace the *first instance* of a string in .NET?. If instead you only and always want to remove the first character, see Fastest way to remove first char in a string. If you want to remove specific characters from the start of the string, see C# TrimStart with string parameter.
No, Replace method replace all occurrencies of a char in the string (see https://msdn.microsoft.com/en-us/library/fk49wtc1(v=vs.110).aspx).
If you need to remove just fist/last char (if any) you can use Trim function: https://msdn.microsoft.com/en-us/library/d4tt83f9(v=vs.110).aspx
in your case:
result[i, 0] = result[i, 0].Trim('"')
Your requirement works with this.
string strTest = "\"NewClient\"Name\"";
strTest = strTest.TrimStart('"');
which in your case it is
result[i, 0] = result[i, 0].TrimStart('"');
*Replace will remove and replace all matching char/string in the given instance.
