Error: Input string was not in a correct format.

How to avoid Error "Input string was not in a correct format"

To avoid error always make check whether you are passing a valid value to function.

Example:

Code Contain Error
protected void Page_Load(object sender, EventArgs e)
{
string str1 = "3.5";
string str2 = "";

//Here we know that str2 is blank, but when values are assigned dynamic it is
//Best practise to make check before passing value to function.
TestFn(float.Parse(str1),float.Parse(str2));
}

private void TestFn(float value1, float value2)
{
//Do Something...
}


Code with Check to Avoid Error
protected void Page_Load(object sender, EventArgs e)
{
string str1 = "3.5";
string str2 = "";

float fStr1;
if (str1 != string.Empty)
fStr1 = float.Parse(str1);
else
fStr1 = 0;

float fStr2;
if (str2 != string.Empty)
fStr2 = float.Parse(str2);
else
fStr2 = 0;

//Values are parse and check for validity before passing to function
TestFn(fStr1,fStr2);
}

private void TestFn(float value1, float value2)
{
//Do Something...
}

Note: Code is just for example and has practically of no meaning.