Visual basic text file manipulation

It is an inefficient method to append text to the control, especially if the control contains a lot of text already. Now, you can use the AppendText method to append strings to the control, which is far more efficient than manipulating the Text property directly.

To append a string to a TextBox control, use the following statement:. The AppendText method appends the specified text to the control as is, without any line breaks between successive calls. In addition to the Text property, you can access the text on the control by using the Lines property. The Lines property is a string array, and each element holds a paragraph of text. The first paragraph is stored in the element Lines 0 , the second paragraph in the element Lines 1 , and so on.

You can iterate through the text lines with a loop such as the following:. You must replace the line in brackets with the appropriate code, of course. Because the Lines property is an array, it supports the GetUpperBound method, which returns the index of the last element in the array.

Skip to main content Skip to primary sidebar Skip to secondary sidebar. IndexOf "Visual". The strings that are returned by the GetFiles method are then added to the ListBox.

Run the application. Click the Browse button. In the Browse For Folder dialog box, browse to a folder that contains. Create a Click event handler for examineButton by double-clicking the control on the form. The code verifies that an item is selected in the ListBox. It then obtains the file path entry from the ListBox. The FileExists method is used to check whether the file still exists. The file path is sent as an argument to the GetTextForOutput method, which is added in the next step.

This method returns a string that contains file information. The file information appears in a MessageBox. The code uses the GetFileInfo method to obtain file parameters. The file parameters are added to a StringBuilder. The first line of the contents is obtained from the StreamReader and is added to the StringBuilder. Click Browse , and browse to a folder that contains. Click OK. Select a file in the ListBox , and then click Examine. A MessageBox shows the file information.

The code sets the log file path to put the log file in the same directory as that of the selected file. The text of the log entry is set to the current date and time followed by the file information. The WriteAllText method, with the append argument set to True , is used to create the log entry.

With the StreamReader object, you can then read the file. File Dim oRead as System. StreamWriter class for writing to the text file are Write and WriteLine.

The difference between these methods is that the WriteLine method appends a newline character at the end of the line while the Write method does not. Both of these methods are overloaded to write various data types and to write formatted text to the file.

The following example demonstrates how to use the WriteLine method: oWrite. The ability to format the output has been significantly improved over previous versions of Visual Basic. There are several overloaded methods for producing formatted text. Close The overloaded method used in these examples accepts a string to be formatted and then a parameter array of values to be used in the formatted string. The first line writes a header for our report.

Each curly brace set consists of two numbers. The first number is the index of the item to be displayed in the parameter array. Notice that the parameter array is zero based. The second number represents the size of the field in which the parameter will be printed.

Alignment of the field can also be defined; positive values are left aligned and negative values are right aligned.

The second line demonstrates how to format values of various data types. The second field will output the current time formatted as PM. The third field will format the value So if the local machine were set for U. Listing A shows the output of our sample code. Reading from a text file The System. StreamReader class supports several methods for reading text files and offers a way of determining whether you are at the end of the file that's different from previous versions of Visual Basic.

Line-by-line Reading a text file line-by-line is straightforward.