Skip to main content

How to Resolve Error "CS1010: Newline in constant" in C#

The Compiler Error CS1010 is a syntax error regarding String Literals. The message reads: "Newline in constant".

In C#, a standard string literal starts with a double quote " and must end with a double quote " on the same line. The compiler reads code line-by-line; if it reaches the end of a line and hasn't found the closing quote for a string, it assumes you forgot it (or formatted the string incorrectly) and throws CS1010.

This guide explains how to handle multi-line text correctly in C#.

Understanding String Literals​

  • Standard String ("..."): Must be on a single line. Backslashes (\) are treated as escape characters.
  • Verbatim String (@"..."): Can span multiple lines. Backslashes are treated literally.
  • Raw String ("""..."""): Can span multiple lines and allows unescaped quotes (C# 11+).

CS1010 appears when you try to force a Standard String to behave like a Verbatim or Raw string.

Scenario 1: Missing Closing Quote or Accidental Line Break​

This is the most common cause. You started typing a string, pressed Enter, and continued typing on the next line. Standard strings do not support literal newlines.

Example of error​

public class Program
{
    static void Main()
    {
        // ⛔️ Error CS1010: Newline in constant
        // The compiler hits the end of line 6 without seeing a closing quote.
        string message = "Hello
        World"; 
    }
}

Solution: Concatenation​

If you broke the line just to make your code look readable (but you don't actually want a newline in the resulting text), close the string on the first line and use the concatenation operator +.

public class Program
{
    static void Main()
    {
        // ✅ Correct: Two valid string literals joined together.
        string message = "Hello " +
                         "World";
    }
}
note

If you actually want a newline character in the output, use the escape sequence \n inside the single-line string: "Hello\nWorld".

Scenario 2: Intentionally Multi-line Strings (Verbatim)​

If you are pasting a large block of text (like a SQL query, JSON, or XML) and you want the newlines to be preserved in the string variable, you cannot use standard quotes.

Example of error​

public void RunQuery()
{
    // ⛔️ Error CS1010: Standard strings cannot span lines.
    string sql = "SELECT * 
                  FROM Users
                  WHERE Id = 1";
}

Solution: Verbatim Strings (@)​

Add the @ symbol before the opening quote. This tells the compiler to accept newlines as part of the string data.

public void RunQuery()
{
    // ✅ Correct: The '@' symbol allows multi-line content.
    string sql = @"SELECT * 
                   FROM Users
                   WHERE Id = 1";
                   
    System.Console.WriteLine(sql);
}

Scenario 3: Raw String Literals (C# 11+)​

If you are using .NET 7 / C# 11 or newer, you have access to a cleaner syntax called Raw String Literals. This uses three (or more) double quotes. It is superior to Verbatim strings because it allows you to indent your code without adding that indentation to the actual string value.

Solution: use triple quotes """ to start and end the block.

public void GetHtml()
{
    // ✅ Correct: Raw string literal.
    // The whitespace to the left of the closing """ is ignored.
    string html = """
        <html>
            <body>
                <h1>Hello</h1>
            </body>
        </html>
        """;
}

Conclusion​

CS1010 is the compiler saying: "You pressed Enter before finishing your sentence."

  1. Check for Typos: Did you forget to close a string with "?
  2. Code Formatting: If splitting a long line of code, close the string and use +.
  3. Multi-line Text: If you need the text itself to have lines, use @" (Verbatim) or """ (Raw Strings).

Table of Contents